The 18-year-old was the second person arrested in the homicide case, which police now say was connected to a marijuana robbery.
Previously arrested was the 18-year-old suspected shooter and Richmond resident on Aug. 24.
The newly arrested suspect is accused of being the getaway driver and was allegedly found Monday in possession of an illegal assault weapon and high-capacity magazine.
PREVIOUS: Man fatally shot at parking lot in El Cerrito shopping center; police searching for 2 suspects
Police officers from multiple departments responded to the shooting at El Cerrito's Del Norte Plaza at 11299 San Pablo Ave. at about 12:23 p.m. on Aug. 23, according to the El Cerrito Police Department.
Witnesses told police that a young man was involved in an altercation with two men near his car, which was parked near the Los Moles Beer Garden restaurant. Police allege the victim had been set up by his assailants, who planned on robbing him.
The victim was found by police suffering from gunshot wounds. He was pronounced dead at the scene.
The two alleged shooters fled in a dark sedan, police said.
On Aug. 24, Richmond officers located one of the suspected shooters, and he was taken into custody by El Cerrito police and booked into jail on suspicion of murder and robbery. A search of his residence was also carried out.
The vehicle allegedly tied to the suspects was located on Monday night, a 2017 Nissan Maxima.
One suspect still remains outstanding, according to police.
Anyone with information was asked to contact the El Cerrito Police Department, which is leading the homicide investigation, at 510-237-3233.