A former college chemistry graduate student has been arrested and charged with multiple counts of battery and possession of a controlled substance after a surveillance camera caught him apparently injecting an substance into the doorframe of his neighbor’s apartment.

Umar Abdullah told WTVT that Xuming Li, who lived below him and his family, began complaining about noises, which Abdullah said he eventually came to believe didn’t exist.

“He complained about footsteps. He complained about door closing sounds,” Abdullah said. “My landlord and I did a simulation, and we could hardly find any sound.”

After months of back and forth texts, Abdullah said, his family began feeling sick in May and noticed an odd smell in the house. He had appliances checked, air vents, everything he could think of, but found nothing. The smell returned in June. He installed a camera in a plant outside his door and was surprised when the video captured Li crouching by the door and doing something — it wasn’t clear what because of the angle. So Abdullah adjusted the camera.

This time, the video showed Li crouching by the door, taking out a syringe, filling it with a liquid, then injecting it into a crack in the doorframe.

Abdullah went to police, and Li was arrested. WFLA said that Tampa Police conducted a hazmat test on the “liquid chemical agent” and found that it contained the opioid pain medications methodone and hydrocodone.

Li’s arrest record says he is a student at the University of South Florida, but the school told the station he is no longer enrolled and that his last semester was this summer.

Li is out on bond and is due back in court on December 5. He pleaded not guilty.

Abdullah says he and his family — his wife and 1-year-old daughter — are looking for a new home.

For the latest true crime and justice news, subscribe to the ‘Crime Stories with Nancy Grace’ podcast.

[Featured image: Umar Abdullah via WTVT]