The victim was inside Perry Traditional Academy in Pittsburgh when the unprovoked attack happened. She was treated for second-degree burns to her knee.
According to a police criminal complaint, Allen had a lighter and was walking down the hallway. The other student was actually talking to the assistant principal when police said Allen bent down and lit her pants on fire.
The principal helped the victim put the fire out, but the damage had been done.
School police said Allen lit the student's frayed jeans on her right knee, and she was treated for second-degree burns.
WPXI reached out to the district, but officials could only say they are “unable to share information related to an ongoing investigation involving a student.”
Investigators also said the incident was caught on the school’s security cameras, and police have entered that as evidence in the case.
Allen is facing aggravated assault, reckless endangerment and arson charges. It's unclear if he is still in school.
He is awaiting a preliminary hearing on those charges.