The man's identity has not yet been released by the medical examiner's office.
The man, who was in his 50s according to police, was detained by police at Greenwich Street and Van Ness Avenue at about 3:20 p.m. after officers responded to a report that he was illegally panhandling in the median there, according to police spokesman Sgt. Steve Mannina.
The man escaped and fled eastbound on Greenwich Street, according to Mannina. He then pulled a kitchen knife with an approximately 8-inch blade after being stopped by three officers at Greenwich and Polk Streets, Mannina said.
The officers ordered him to drop the knife but he refused and instead lunged at one of the officers with the weapon, according to Mannina.
One of the officers responded by firing at the man, who was struck at least once, Mannina said.
None of the officers were injured, according to Mannina.
The officers reportedly administered medical attention until an ambulance arrived and transported him to San Francisco General Hospital, where he died shortly before 7 p.m., Mannina said.
The officer who fired the shots, a veteran according to Mannina, has been placed on routine administrative leave while the incident is being investigated by police and the San Francisco District Attorney's Office.
