A Florida man has been charged with several counts of battery after injecting a potentially hazardous chemical into his upstairs neighbors' home.

After a hidden camera showed Xuming Li using a syringe to inject a chemical into the bottom of a door, he was charged with three counts of battery for dispersed chemical agent, possession of a controlled substances, aggravated stalking and battery on law enforcement via the chemical agent, according to the arrest affidavit out of Hillsborough County.

Li was a doctorate student in the chemistry department at the University of Florida between 2018 and the summer of 2023, according to a USF spokesperson. He has pleaded not guilty to the charges and his attorney declined to comment further on the matter.

In an interview with USA TODAY, Umar Abdullah outlined the year of conflict with his downstairs neighbor, Li, leading up to the video that got him arrested.

Abdullah said he received endless noise complaints almost immediately after moving into his Tampa apartment last year. The complaints picked up in August 2022 when Abdullah's daughter was born, but they weren't about the baby crying.

"He was complaining about footsteps, drawers, Roomba–like all the various sounds that you do in an apartment," Abdullah said.

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Li went to the landlord, called the police and complained to the HOA about the noise, according to Abdullah.

On May 31, Abdullah had a friend drop by his house to check on a delivery he received while he was out of town. After she arrived, she called him and asked if he had painted or bought new furniture recently because it smelled strongly of chemicals and made her eyes burn. When he replied no, she said she had to leave because it felt like someone threw chili powder on her.

That was the first of several incidents when his family would experience the mystery smell that seemed to be coming from the water heater closet next to the front door. Abdullah said they called Tampa Fire Recue on one occasion to check for chemical leaks, but found nothing. They had the AC checked and water heater replaced, but neither solved the issue.

Meanwhile, every time the smell would appear, his daughter's eyes would water and she would cough until she vomited. After eliminating several potential sources of the smell, him and his wife began to suspect someone was tampering with their home.

"I started sniffing the water heater area like a dog, and as I was moving towards the entry door from the water heater door, I felt that the smell is even more severe, a toxic smell," he said. "And the headache–I can't describe in words. It is so bad."

In June, he set up the camera and captured Li in the act on two back-to-back days. The first video wasn't clear what was happening. The second time when the syringe was visible, he called the police.

Li's arrest affidavit shows that the fire rescue respondents also experienced skin irritation after their first visit, but did not know the cause at the time.

Early testing of the chemical showed methadone and hydrocodone. The USF spokesperson Kevin Watler said that the university's chemistry labs do not have controlled substances.

"The safety and well-being of the USF community is our highest priority," Watler's emailed statement on behalf of USF reads. "The USF Department of Chemistry has several safeguards in place to ensure all chemicals and other materials owned by the university for teaching and research purposes are accounted for and used properly. "

Abdullah said his family is no longer suffering medically, but he hopes that final testing of the chemical comes back with different results anyways.

"I still pray and hope that the final lab report says that the chemical is something different, that is something inauthentic and not something hazardous. Because I care for my family, and I just don't want any harm for my daughter."