Riley Strain's family is expressing frustration toward his fraternity brothers. 

Nearly a month after the University of Missouri student's body was found in Nashville's Cumberland River, his mom Michelle Whiteid criticized the Delta Chi brothers' response. Specifically, she questioned why the fraternity members who were in Nashville with Riley when he went missing March 8, had not called the police when they informed her he had vanished.  

"Why wouldn't they have called the police when they got back at 3:15 in the morning and didn't see him then?" Michelle said during a joint appearance with her husband Chris Whiteid, Riley's father Ryan Gilbert and stepmother Milli Gilbert on NewsNation April 16. "I don't know."

And Chris emphasized that the fraternity brothers did not involve the authorities until nearly 14 hours after his stepson was last seen. 

"We called them on the way down," he explained. "It was probably close to 12 o'clock and they were just going to the Sheriff's office to report him missing."

Michelle and Chris also felt abandoned by Riley's friends soon after their March 9 arrival in Nashville.

"So when we got there, several of the boys were out front with a police officer," Michelle continued. "The boys stayed out for a while and then they all of a sudden disappeared."

Noting the frat's plans to continue with the event that brought them to Nashville, she tearily continued, "They ended up back out a little while later in their dress clothes to go out to their formal that night."

Chris recalled that he and Michelle went out to conduct their own search through several Nashville hospitals for hours before returning to the hotel where Riley's fraternity had been staying. 

"We come back and they're coming back, some of them from the party and they're waving at us as we're sitting in the truck," he added. "How does that make you feel?"

And while Chris added that the fraternity brothers initially offered their support, they did not follow through in helping the family. 

"We didn't know what we needed at that point in time," he expressed. "But you would've thought that they would've at least been out searching, trying to do something. It wasn't."

Riley's father Ryan added, "We weren't very happy with them to say the least. It's appalling." 

In the near month since the search for Riley concluded, Michelle said the family still has not had a formal conversation with her son's fraternity brothers, and she feels like the organization "maybe" has information they have not disclosed about the night Riley disappeared. 

"I haven't sat down and talked to any of them to say ‘Tell me your whole entire story,'" she said. "Would I like that? Yes. It would be nice."

And Chris interjected, "I don't understand why they wouldn't have reached out to us, wanting to provide information from that night. Maybe I'm crazy, but why should we have to reach out to them and beg them for information on a missing brother?"

Read on for a full timeline of the family's search for answers regarding Riley's disappearance and death. 

E! News has reached out to University of Missouri and its Delta Chi chapter for comment but has not heard back. 

Riley Strain, 22, a business and financial planning major at the University of Missouri, was among a big group of Delta Chi fraternity brothers that arrived in Nashville by bus on Friday, March 8.

They checked into The Tempo hotel on Rosa L. Parks Boulevard, a short walk to the nightlife on Broadway.

"When they left Tempo, the went down to, I believe, Miranda Lambert's bar [Casa Rosa] first, spent probably about an hour and 15 minutes or so, maybe a little longer, there," Riley's stepdad Chris Whiteid later told NBC affiliate WSMV 4, describing what he knew of Riley's whereabouts before he went missing. Then the group went to the Garth Brooks-owned Friends in Low Places Bar & Honky Tonk, where Riley FaceTimed his mom, Michelle Whiteid, at around 7:30 p.m. 

"I said, 'Have fun, be careful, I love you,'" Michelle told WSMV. "I got an 'I love you' and that's the last I heard."

Chris explained that he overheard Riley detailing his evening to Michelle. "He didn't even sound like he had been drinking a lot," Chris told NBC News, adding that Riley continued to text with his mom for another hour or so after they spoke. 

Riley's stepdad also speculated whether he could have been drugged, because "we're hearing the horror stories" about that happening to people.

After Friends in Low Places, Riley and his group went next to Luke Bryan's Luke's 32 Bridge Food + Drink.

The Tennessee Alcoholic Beverage Commission confirmed March 14 it was investigating whether Riley arrived at Luke's 32 Bridge "visibly intoxicated" and was overserved. 

The bar maintained in a statement that Riley bought one drink and two waters before he was asked to leave at 9:35 p.m., "based on our conduct standards," and escorted out through the front exit on Broadway. The business, which also noted that it was cooperating with the police and the TABC, stated that a member of Riley's party accompanied him downstairs to the door but then went back upstairs to the bar when Riley left.

"Y'all this is scary," Luke Bryan wrote while also sharing the restaurant's statement to his Instagram Story. "Praying for his safe return."

The TABC told E! News in a statement April 1 that it's "investigating multiple places" to determine whether a violation of state alcohol law occurred at any of the establishments where Riley was served alcohol on March 8.

"All licensed establishments questioned have been cooperative," the agency said. "The final report will be made public once the investigation has been closed."

Riley's mother later recalled a text Riley had sent her March 8 regarding the taste of a rum and coke he had at one of the bars, saying it tasted like barbecue. 

She noted, "Maybe there was something in it that shouldn't have been."

It wasn't Riley's first time in Nashville, according to his stepdad.

But he and his friends "got separated," Chris told WSMV on March 11. "The boys called him, and he said I'm walking back to my hotel. They didn't think anything about it." 

But a security camera outside an escape room business captured Riley on Third Avenue North cutting across a parking lot and going in a different direction. Another camera recorded him on Gay Street crossing First Avenue North at 9:47 p.m. 

Upon reaching the corner, he stopped and, staggering a bit, looked back in the direction he'd just come from before continuing down the street. (Police shared both videos on social media during the investigation.)

Chris said they wanted to see "what was happening before the parking lot, and we'd also like to know what happened after he crossed down onto Gay Street because there's such a void that we haven't seen. There's something there that's going to fill some gaps."

Riley's father, Ryan Gilbert, told WSMV, "He made it as far as we know, basically to the James Robertson [Parkway] Bridge, and that's the critical time where things went dark." The last Life360 ping from Riley's phone came from near the bridge, which crosses the Cumberland River, according to his parents and stepdad.

According to what Riley's friends told Chris, as he detailed to WSMV, when the rest of the group got back to the hotel that night and saw he wasn't there, they went back out to look for him and tried to track him using Snapchat locations. When that proved fruitless, and then Riley wasn't to be found in any of the other rooms where roughly 30 members of the fraternity were staying, the guys called Chris and Michelle.

He and Riley's mom jumped in the car, Chris said, and drove straight to Nashville from Springfield, Mo. In an April 16 interview with NewsNation, Riley's family emphasized that 14 hours passed before the fraternity reported Riley missing to the authorities. 

Police said they responded to the Tempo hotel March 9 in response to a call about a missing person. A friend of Riley's called 911 and told the dispatcher one of his "good buddies" was missing, according to a recording of the call obtained by WKRN. The caller said Riley's last phone location was near the river at 11 p.m.

"When we got into town Saturday evening, we met with an [MNPD] officer and he has been amazing as far as I'm concerned," Chris told WKRN. "He made phone calls, he radioed people to go check locations while he was with us. He was also making phone calls and he sent the report out and it hit the national database. I felt like things were handled very well, and he was very helpful."

A police report reviewed by CNN noted that Verizon Wireless determined the last ping from Riley's phone was .64 miles southwest of a cell tower located at 19 Oldham Street, near the river, but a search of the area came up empty.

"We talk every day, multiple times a day," Michelle told WSMV three days into the search. "This is the longest I've ever gone without talking to him."

Chris described his stepson as "a very identifiable young man" who was 6-foot-7, with blond hair and blue eyes. "We're in a bad dream," he said. "Can we wake up? Please, just let us wake up."

Added Michelle, "Oh, God, bud, we love you so much and we're all looking for you, all of us. If anybody knows anything, please just call the police."

On March 17, police shared that two women who were voluntarily aiding in the search found Riley's bank card on the embankment between Gay Street and the Cumberland River.

The next day, police shared the latest video they'd obtained of Riley on the night of March 8: He had a brief interaction with a cop responding to a vehicle burglary on Gay Street, on a sidewalk adjacent to the Cumberland River, at 9:52 p.m.

The officer, who was wearing a body cam, can be heard asking Riley how he's doing, to which the young man replied, "I'm good, how are you?" and kept walking.

"To those who are saying that they believe he could have been in distress, that somebody could have been after him as he walked onto Gay Street," said police spokesman Don Aaron, "well, as you see in the video, he's walking by himself on the river side and speaks to a police officer as the officer is looking at a vehicle that had been broken into."

So far, the officer said, they had found no evidence to suggest Riley had been a victim of foul play.

Stepdad Chris told NBC News the family had been able to access all of Riley's accounts except for the one linked to the bank card, and that there had been no credit or debit charges on any of them during the search.

"I want Riley to know: We're actively looking for you, son," he said. "We're going to bring you home."

Chris shared during a March 19 press conference that the family was getting an assist from the United Cajun Navy, a volunteer-based disaster response agency. 

"We appreciate more than you'll ever know the outpouring that we've received from the community, from the press and everyone else involved," he said. "Our goal is still to bring Riley home. We feel that is still a very viable goal. We feel like Dave [David Flagg, national director of operations for the UCN], his team and the volunteers that he knows are very skilled and will help bring this for us."

MNPD Sgt. Robert Nielsen also stressed to the media that they were continuing to follow up on tips and doing everything they could to find Riley.

On March 20, the Cheatham County Sheriff's Office oversaw what they described as a "basic shutdown" at the Cheatham Lock and Dam, where the Cumberland River flows into Cheatham Lake, in connection with the search. Investigators sifted through debris that subsequently floated to the surface, according to WKRN.

Riley's dad Ryan was also out on a different part of the river that day, the station reported, on a boat with the United Cajun Navy.

"I've got to be here," he told WKRN. "I've got to be on the water. I wanted to be on the water last week, and we had some other family members that took that role that day. But I'm glad to be out here because I want to be here, I want to be the one that finds him."

At 7:28 a.m. on March 22, a local worker called police to report seeing a body in the Cumberland River in Western Nashville, Metropolitan Nashville Police Chief John Drake said at a press conference later that day.

The Davidson County Medical Examiner's Office positively identified Riley, but his black and white shirt and other identifiable objects on the body, including a watch, also indicated it was him, according to the chief.

"I want to say to the family, my heart and prayers go out to you all for this very unfortunate and tragic incident," the chief said. "I also want to say thank you to the Nashville community and the outpouring of support from the community in trying to help us locate Mr. Strain."

Factoring in his height and weight, investigators had estimated when and where Riley's body might surface if he'd gone into the river. "This is the 14th day," the chief explained, "so we were really expecting anytime soon to find him. So we were in the right spot. It's just unfortunate."

He said there was "no other evidence to suggest anything other than" that Riley fell into the river.

Riley's dad, mom and stepfather all wore green, his favorite color, to police headquarters that afternoon, according to WKRN. 

Speaking to reporters, Michelle said, "I just ask that you mommas out there, hug your babies tight tonight please. Please, for me, just hug your babies tight tonight. And again, thank you, thank you for sharing our story."

An autopsy was performed March 23. Police confirmed to E! News that a detective was present for the postmortem and cause of death continued to appear accidental, with no signs of foul play-related trauma. Toxicology results are still pending.

In the meantime, Riley's family hired a private company to perform an independent autopsy, family friend Chris Dingman told NewsNation on March 27.

"The original autopsy came out just like theirs did with, you know, no obvious signs of trauma, as in weapons, guns or knives or etc.," he said. "But they were able to do a little bit more testing on specific items." He also referred to a police report that stated Riley didn't have on his jeans or his boots, and his wallet wasn't recovered.

Another thing that "threw the family for a loop," Chris Dingman continued, "was the coroner going on record with a news person in Nashville stating about the lack of water in his lungs. It raises more questions, you know? I'm not a crime drama person by no means, but usually water in the lungs means that, you know, they were alive when they went into the water."

The family then went about the rituals of mourning: A visitation and celebration of life were held March 29 at Greenlawn Funeral Home in Springfield,Mo. According to an online obituary paying tribute to Riley's "vibrant spirit and loving nature," they're planning a private burial.

The family requested that attendees wear something green and dress comfortably, "to honor Riley's love of life."

Weeks after Riley's body was found, his family is determined to find the cause of the 22-year-old's death. They also spoke out against how his fraternity responded to his disappearance, and noted they still haven't provided adequate details of the night of March 8. 

 “I don’t understand why they wouldn’t have reached out to us, wanting to provide information from that night," Chris said. "Maybe I’m crazy, but why should we have to reach out to them and beg them for information on a missing brother?”

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