The man's arm had been covered with a towel, and he had waved down police at the top of the hill on busy Los Feliz Boulevard, the busy seven-lane avenue linking Glendale and Hollywood.
His name has not been released.
No weapon was recovered from the shooting scene, near the intersection of Los Feliz at Tica Drive, said Los Angeles police officer Rosario Herrera of the Media Relations Section.
Herrera said officers in a patrol vehicle were eastbound on Los Feliz at 6:25 p.m. Friday when the suspect, as a pedestrian, was walking and yelling "police, police."
LAPD Lt. John Jenal told reporters at the scene the suspect had waved down officers as they were on patrol in the Griffith Park area.
The suspect then extended his arm, which was covered with a towel, toward the officers. The suspect was told twice to drop his gun, and then was shot, Jenal said.
"Their perception was there was a gun,'' Jenal told news outlets.
A witness told one TV station that he heard four pops at the time of the shooting.