The man was pronounced dead at the scene after the 1:15 a.m. shooting.
A report of a disturbance sent officers to the Infusion Lounge, a nightclub at the shopping and entertainment complex outside the Universal Studios tourist attraction.
The club was hosting a disc jockey contest when a fight broke out and spilled outside, DJ Phil told KCBS-TV (http://cbsloc.al/1hHc6o9 )
"A lot of guys were rumbling and fighting and of course, you know, they start throwing bottles and this escalated and gunshots rang out," the disc jockey said.
Arriving officers saw a crowd outside the lounge, heard shots and saw a man with a gun, Sgt. Barry Montgomery said. They opened fire, killing him. His name wasn't immediately released.
A gun was recovered.
Four people received minor injuries while trying to escape in the panicked, fleeing crowd, authorities said.
No officers were hurt.