Two friends thought they were playing with an unloaded gun at a Silver Terrace home earlier this month when one of them fired a shot into the back of the other’s head, killing him, the shooter’s attorney said Wednesday.

The 15-year-old boy accused in the April 9 killing of Andy Zeng, 16, appeared in juvenile court Wednesday morning but once again postponed entering a plea to murder on the advice of his new attorney, Tony Tamburello, who said he is still reviewing evidence in the case.

Tamburello said following the brief hearing that the initial police reports “indicate that there was no malice or premeditation involved.”

“It was more akin with an event that happened with what was thought to be an unloaded gun,” he said.

The teen suspect, who The Examiner is not naming because he is a minor, shot Zeng with a .22-caliber handgun when they were alone at the unnamed boy’s home at 2138 Quesada Ave., according to police and prosecutors. He then allegedly phoned other friends to help dispose of Zeng’s body. Upstairs neighbors called police when they smelled gas that the teens allegedly poured on the floor in a failed attempt to burn the body.

Tamburello said the shooting was either a complete accident or “a careless mistake,” but not murder.

“He is extremely sorry and expresses a great deal of remorse,” said Tamburello of his client. “Andy was his good friend.”

aburack@sfexaminer.com