A Danvers teen is guilty of raping and murdering his high school math teacher in 2013 then disposing of her body in a wooded area, a jury ruled Tuesday, the Boston Globe reported.

Philip Chism was charged as an adult in the murder of Colleen Ritzer, 24, who had been a popular teacher in Danvers, about 20 miles north of Boston.

He faces a mandatory sentence of life in prison without parole.

Chism's attorney had argued that Chism, a freshman at the time, attacked Ritzer on Oct. 22, 2013, due to mental illness, but prosecutors painted the teen as a remorseless killer.

Prosecutors said Chism followed Ritzer into the bathroom after school, raped her, cut her throat with a box cutter and transported her body off campus in a recycling receptacle.

Chism also stole Ritzer’s credit card, which prosecutors say he used to buy fast food and a ticket to a movie at a mall.

Chism was acquitted of raping Ritzer with a tree branch in the woods, the Globe reported.

A Topsfield police officer who found Chism walking along a rural road the night of Oct. 22 testified that he noticed blood on Chism’s clothing after bringing him to the police station.

Reuters contributed to this report.