An internal investigation into a former Boston high school dean who stands accused of shooting a teen in the head over a drug dispute has found the school district acted justly in reprimanding the dean on three different occasions.

However, the incident has triggered the school district’s interim superintendent to order an external audit of the matter and a review of the district’s disciplinary policies.

Police allege Shaun Harrison, 55, a former dean of Boston English High School shot a 17-year-old over a marijuana dispute earlier this month. Prosecutors alleged Harrison, a reverend and noted anti-gang activist, ran a marijuana ring and used the victim to sell drugs for him. The shooting allegedly occurred on March 3; he was fired from his position on March 5.

He was fired in early March from his position as dean. Boston Public Schools consequently launched an internal investigation. The findings of the investigation released Tuesday stated that he was formally disciplined on three occasions during the course of his employment with the district.

Two of the instances occurred in November 2012, when he was a community field coordinator at Boston Green Academy. Harrison was alleged to have pushed a female student before throwing a roll of tape at her. That month, he was also alleged to have made inappropriate statements regarding recreational drug use to two students. He received written reprimands for both those instances.

On March 3, at English High, the school district alleges Harrison was “engaged in an altercation with a female student” during which he pushed her and told her he would “smack the (expletive) out of you.” After an investigation, it was recommended the school fire Harrison, which they did on March 5.

The school district’s office of labor relations found the school acted correctly in all three incidents. That office, however, is recommending that an outside entity review the district’s procedures for disciplinary investigations “with the goal of more stringent guidelines for higher standards of performance and conduct by employees.”

“I’ve directed that a complete and external independent review of our district’s policies and protocols related to employee discipline be undertaken,” said Boston Public Schools Interim Superintendent John McDonough in a statement. “While our internal investigation appears to have found that proper protocols were followed, I remain unconvinced that our standards are high enough to meet the basic expectations of the students and families we serve.”

He added, “The results of this internal investigation confirm quite clearly for me that our protocols must reflect that a higher standard is being reached. We must also create an environment that provides students and staff with a mechanism to report instances of conduct unbecoming of BPS staff confidentially, and, in some cases, anonymously. Our students and families deserve better and we will do better.”