ANAHEIM (AP) -- Demonstrators stormed a police department in Orange County on Sunday to protest an officer-involved shooting Saturday night that left an unarmed man dead and led to a violent clash between witnesses and police.

A crowd swarmed the Anaheim police headquarters' lobby Sunday as Chief John Welter held a news conference to discuss what happened the night before. The protesters chanted "no justice, no peace" and "cops, pigs, murderers" as officers stood by and watched.

Welter said two officers were placed on paid leave after one of them fatally shot 24-year-old Manuel Diaz.

He said the officers approached three men in an alleyway when they ran away. One of the officers chased Diaz to the front of an apartment complex, where the shooting occurred.

Welter would not say what led the officer to shoot Diaz, citing an independent investigation by the district attorney's office. Police said Diaz was a known gang member.

Mayor Tom Tait said he will ask the state attorney general to assist in the probe. "Transparency is essential. Whatever the truth is, we will own it," Tait said.

The shooting sparked a melee in the neighborhood as some threw rocks and bottles at officers who were securing the scene for investigators to collect evidence. Sgt. Bob Dunn, the department's spokesman, said that as officers detained an instigator, the crowd advanced on officers, who fired bean bags and pepper balls at them.

Video