The shooting happened just before 2:45 a.m. at the El Rodeo nightclub on the 8800 block of Washington Boulevard.
Los Angeles County sheriff's officials said two men were shot at the club and taken to a hospital. One of the men, who authorities identified as a valet, later died. The other victim, a security guard, was last listed in stable condition.
Witnesses say the gunman was a patron at the club, who was causing trouble and escorted out. He then returned, and when security stopped him, he went to his car, got a gun and shot the two men.
The suspect was captured after a short chase. Four other people have been detained.
The names of the suspects and victims have not been released.
Anyone with information about this incident was asked to contact the Los Angeles County Sheriff's Department's Homicide Bureau at (323) 890-5500.