A second teenager charged in the assault and robbery of an 18-year-old actor earlier this month on a San Francisco Municipal Railway bus pleaded not guilty to the charges this morning in San Francisco Superior Court, according to the district attorney’s office.

Fagamalama Pasene, 16, who is being charged as an adult, pleaded not guilty at his arraignment Tuesday to felony charges of second-degree robbery, assault with force likely to cause great bodily injury and assault on a bus passenger.

He was arrested last week in connection with the assault on Christopher Borgzinner on a 9-San Bruno bus at 5:45 p.m. on Oct. 5. Uluao Mase, 18, and a third suspect, a juvenile, were also arrested last week for the crime. Police are still seeking a fourth suspect.

Mase pleaded not guilty at his arraignment Monday to charges of robbery, assault and possession of an assault weapon, a gun that was found in his backpack but was apparently not used in the alleged crime.

Mase and Pasene had bail set at $200,000 and both are scheduled to appear at a preliminary hearing Nov. 2.

Police credited the arrests to surveillance footage taken from a video camera on the bus.

The attack left Borgzinner with a fractured orbital socket, cheekbone and jaw, according to prosecutors.

Police and prosecutors said Mase confronted Borgzinner on the bus and asked to use his cell phone. Mase, Pasene and the other suspects then asked if Borgzinner belonged to a gang before assaulting him and stealing his iPod and wallet.

Borgzinner, a San Francisco resident, has no gang affiliation, police said. He plays “Nacho” in the upcoming film “La Mission,” starring Benjamin Bratt and directed by Bratt’s brother Peter Bratt. The film was shot in San Francisco’s Mission District.

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