BOSTON (AP) — A 15-year-old Massachusetts boy charged with killing his teacher last year faces new charges after an assault on a state youth services staffer.

Prosecutors said Wednesday that Philip Chism has been indicted as a youthful offender on charges of attempted murder by strangulation, assault with intent to murder, kidnapping, and assault and battery with a dangerous weapon. He could face adult penalties if convicted.

Prosecutors allege Chism attacked the 29-year-old woman on June 2 after following her into a bathroom at the youth facility in Boston where he was held. Co-workers stopped him when she cried for help. The woman declined medical treatment.

A message was left Wednesday for his lawyer.

Chism has pleaded not guilty to robbing, raping and killing 24-year-old Danvers High School teacher Colleen Ritzer after following her into a school bathroom in October.