Petaluma police said a young man hung himself in an apparent suicide Wednesday night inside a city-owned building across the street from City Hall.
The vacant building, at 417 Western Ave., was formerly the site of the Polly Klaas Performing Arts Center.
Lt. Mike Cook said police received a phone tip at about 7 p.m. from someone who was likely a friend of the victim.
"Officers were sent to do a welfare check on a young man we were told may have been breaking into the building and staying there," Cook said.
Officers then entered the building and found the young man "deceased by apparent suicide," Cook said.
No information was available Thursday about the identity of the young man and it's unclear what city he lived in, Cook said.
City Manager John Brown said there had been no recent reports of squatters occupying the vacant building.