The shooting occurred at approximately 1:20 p.m. at Jim's Burgers in the 200 block of West Adams Boulevard. Authorities say the gunman walked into the restaurant, approached the victim and shot him in the head, then fled on foot.
"By all indications, the victim in this shooting was specifically targeted," said LAPD Lt. Mike Menza. "The shooter ran right out of the restaurant immediately. This whole thing went down in about less than a second."
About two or three shots were fired, according to Menza.
The victim, whose name was not immediately released, was pronounced dead at the scene.
There were about a dozen customers inside the restaurant at the time of the shooting, including women and children.
According to a witness, a confrontation took place inside the restaurant right before the shooting took place. However, a motive has not been established.
Police have not yet released a description of the suspect.