Jimmy Nabong was found guilty of all charges against him, including first-degree murder, murder during a robbery, and use of a firearm, according to the San Mateo County District Attorney's Office.
Shivnesh Reddy, 21, was shot on Oct. 29, 2008, while Nabong and Neil Prakash Chand tried to rob him of money he planned to use to buy marijuana. Nabong allegedly shot Reddy inside a car driven by Chand, according to prosecutors.
His body was later found in the 600 block of First Lane in South San Francisco, police said.
Nabong, who was 17 at the time of the murder, was charged as an adult and was convicted at about 10:45 a.m. Thursday, the second day of jury deliberations, according to prosecutors.
He could face life in prison without the possibility of parole when he is sentenced on May 6.
Chand, 21, pleaded no contest last month for his role in the murder and faces 25 years to life in prison, according to prosecutors.
