Authorities are investigating the suspicious death of a man at his apartment in San Francisco’s Mission district on Thursday, a police spokesman said Friday.

The 74-year-old man, identified by the Medical Examiner’s Office as Joseph Williams, was found dead by police officers who responded to an apartment in the 2900 block of Folsom Street at about 4:50 p.m. Thursday, police Officer Albie Esparza said.

The Medical Examiner’s Office has ruled Williams’ death suspicious, and will be conducting an autopsy Friday to determine what caused his death.

The Police Department’s homicide investigators are also working on the case, Esparza said.

Anyone with information about Williams’ death is encouraged to call the Police Department’s anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.