Detwone D. Watson, 29, of Oakland, is wanted in connection with the shooting and robbery, which occurred at about 1:50 a.m. in the parking lot of the store at 15555 Hesperian Blvd., police said.
Another suspect, Tony Phillips, 20, also of Oakland, was arrested Friday on suspicion of attempted murder and attempted robbery in connection with the crime. Phillips was scheduled to appear in court Tuesday afternoon.
Police have not yet been able to identify the two other suspects.
Sgt. Ted Henderson said that on the morning of Black Friday, Watson and Phillips were passengers in a late 1990s- or early 2000s-model two-door burgundy Buick Riviera that pulled up in the full parking lot behind the three victims, all cousins from San Leandro in their early 20s.
The victims -- Christopher, Rafael and Javier Murillo -- had been standing by their car in the parking lot. They had gone to Walmart in search of a video game, but left the store when they could not find it, police said.
Police said Watson allegedly brandished a gun as he approached Christopher Murillo, and that Phillips allegedly approached Rafael Murillo, who was wearing a gold necklace, and attempted to steal it.
According to police, a fight ensued between Phillips and Rafael Murillo, and Javier Murillo allegedly tried to help his cousin by holding down Phillips. A third suspect exited the Buick and attempted to help Phillips.
Police said that it was then that Watson allegedly shot Christopher Murillo, striking him in the neck.
The third suspect fled on foot, while Watson got back in the Buick and drove off with the driver, leaving Phillips in the custody of the victims, who detained him until police on patrol near the lot arrived and arrested him, Henderson said.
Police said at Tuesday's news conference that their investigation indicated Watson was the shooter and that Christopher Murillo gave Watson and Phillips a $5 bill when the men demanded Rafael Murillo's necklace.
Police said they plan to ask the district attorney's office to charge Watson with attempted murder, two counts of attempted robbery, and one count of robbery.
The driver of the Buick is described as a black man, and the suspect who fled on foot is described as a 6-foot tall, 230-pound black male of unknown age.