BOSTON — A Suffolk Superior Court jury convicted former Boston English High School dean Shaun A. Harrison of assault with intent to murder for shooting 17-year-old high school student Luis Rodriguez, according to U.S. News and World Report. Harrison shot Rodriguez in the back of the head in 2015 and was found guilty of the crime on Thursday.

Harrison, 58, now faces a maximum of 20 years in prison for shooting Rodriguez, which prosecutors say was because of a dispute about weed. Harrison used Rodriguez to sell pot for his marijuana ring, according to authorities, and was upset that he was not selling enough. Harrison also believed Rodriguez was stealing from him.

Police found cocaine and marijuana at the former teacher's residence, as well as drug paraphernalia used to bag and sell drugs, and several guns with ammunition. Authorities also found a shell casing for a 38-caliber pistol.

A Close Call

Authorities said Harrison and Rodriguez were walking down the street when Harrison suddenly pulled out a gun and shot Rodriguez in the back of the head. The incident was caught on a surveillance video.

Rodriguez was able to flag down a car after being shot and was taken to Boston Medical Center, where he spoke to detectives from the Boston Police Department the next day, according to The Washington Post.

Rodriguez survived the attempted murder but now suffers from nerve damage and facial paralysis. He also has hearing loss because of the attack.

The former teacher had previously been an anti-violence advocate.

Harrison was reportedly also in charge of the school substance abuse program and helped homeless students find housing and social workers.

Rodriguez testified against Harrison at the trial and said that that he had trusted his mentor. He said that Harrison was his high school counselor, and that he went to him for help with everything.

Harrison’s lawyer blamed the crime on one of the customers Rodriguez sold drugs to. Harrison is expected to be sentenced at a later date, having also been convicted on several marijuana and firearms charges.

The former teacher was convicted by the Suffolk Superior Court jury after two days of deliberations.