The body of Andy Zeng, a sophomore at Thurgood Marshall Academic High School, was found by police in a home in the 2100 block of Quesada Avenue at about 4:30 a.m. Sunday.
Four teens were initially arrested in connection with the death, but only two have been charged - a 15-year-old boy with murder and 18-year-old Jimmy Lei with being an accessory to murder after the fact.
The teen charged with murder made his first appearance in juvenile court this morning but did not enter a plea.
At Lei's arraignment hearing in San Francisco Superior Court this afternoon, Assistant District Attorney Omid Talai described the grisly details of what he said happened in the hours after Zeng was shot.
Officers had responded early Sunday morning to two 911 calls reporting a smell of gas in the area, Talai said.
They found Zeng partially wrapped in black garbage bags, Talai said.
The landlord of the home where Zeng was found pointed investigators to the 15-year-old's father, who told them his son had admitted to killing someone, according to Talai.
The teen was taken into custody and allegedly described to police how he had accidentally shot Zeng in the back of the head with a .22-caliber revolver, Talai said.
The 15-year-old, whose name is not being released because he is a juvenile, said he called Lei after the shooting, and Lei said he would help him dispose of the body by bringing three or four other people, plus garbage bags and other equipment, Talai said.
Lei allegedly brought garbage bags, latex gloves and three one-gallon canisters of gasoline to the home, and Zeng's body was taken out of the closet where he had been placed, Talai said.
According to Talai, Zeng's body wouldn't fit into the garbage bags, so Lei allegedly recommended cutting him in half, and handed the 15-year-old a butcher knife.
The teen refused, so Lei allegedly recommended maybe breaking Zeng's legs before they decided to pour gas on his body to try to dispose of the evidence, Talai said.
Talai said Lei still smelled like gasoline when police eventually arrested him.
Lei, a student at San Francisco City College, pleaded not guilty to the charges against him, which also include attempted arson and use of an incendiary device.
His defense attorney, Sam Lasser, said outside of court that Lei's "involvement is being seriously overstated," and said he was "maybe at the wrong place at the wrong time."
Judge John Allen ordered Lei be held on $1 million bail. He is scheduled to return to court May 17.
The 15-year-old defendant is set to return to court to be arraigned on April 20. Along with murder, he also faces the charges of attempted arson and use of an incendiary device.
Although Talai said the teen claimed that he shot Zeng accidentally, District Attorney George Gascon told reporters earlier today that "we wouldn't be charging him with murder if we thought it was an accident."
The district attorney's office will not charge the teen as an adult, Gascon said.
After the teen's initial hearing, Zeng's father said through translator Marlene Tran that he wanted more stringent gun and truancy laws, which he said could have saved his only son from being killed.
The father, who did not want to be named, said he did not know the teens arrested in connection with Zeng's death.
He said he hoped "for a fair trial that is expedited so that we can bring closure to the case."
Zeng was "a very good boy, so that's why everyone's in shock," he said.