Three people were detained Thursday in Petaluma in connection with a homicide near Union Square in San Francisco on Wednesday evening.

San Francisco Police Officer Grace Gatpandan would not say what led police to an address on Marshall Avenue in Petaluma, citing only “interviews and evidence from the investigation.”

According to a San Francisco police statement, officers first received a call about an “unconscious person” in the 500 block of Post Street at 6:38 p.m.

“San Francisco Fire Department paramedics had responded and rendered aid, but unfortunately the victim succumbed to his injuries and was pronounced deceased at the scene,” the statement read.

After the San Francisco medical examiner declared the case a homicide, SFPD investigators obtained information that led them to Petaluma. With the help of local law enforcement, San Francisco police investigators obtained a search warrant and the three “persons of interest” were detained, Gatpandan said.

Petaluma police officials said San Francisco police are handling the investigation. Gatpandan would not provide any information about the man who was killed, directing questions to the medical examiner, whose office was closed.

Gatpandan would not say whether the three people were arrested or provide information about their gender or ages.

“Things are done differently here,” she said.

The Bay City News reported Thursday that a man who was killed Wednesday was thought to be about 30 years old.

No other information was available Thursday evening.

Gatpandan said the case is still under investigation and asks anyone with information to call its anonymous tip line at 415-575-4444 or text a tip to TIP411, with SFPD at the beginning of the message.

You can reach Staff Writer Martin Espinoza at 707-521-5213 or On Twitter @renofish.