The shooting was reported shortly after 7:30 p.m. at Pit Boss Barbeque at 12889 San Pablo Ave.
Sgt. Bisa French said the two victims, Intiaz Ahmed, 32, and Alvaro Garcia, 23, were sitting in the bar area having drinks when the four suspects entered the restaurant and someone opened fire.
Ahmed and Garcia were pronounced dead at the scene.
Witnesses told police the suspects were wearing blue clothing, the color associated with the Sureno street gang, French said.
A beat officer familiar with the area knew of a home nearby frequented by Sureno gang members, French said. Officers went to the home and found the suspects along with evidence that they were involved in the shooting, she said.
Several weapons were recovered, including firearms, French said.
Four Richmond residents were arrested for murder. French identified them as Eliseo Flores, 22, Steven Miranda, 20, Ignacio Ruiz, 28, and Victor Torres, 19.
French said police believe the victims had some affiliation with the rival Norteno street gang. Ahmed was a Richmond resident and Garcia had an address in Daly City, according to the Contra Costa County coroner's office.