Hours before a minister and former English High School dean allegedly tried to kill a 17-year-old student in an "execution-style" shooting Tuesday, the preacher incited a fight between two students at the school, according to a law enforcement official briefed on the investigation.
Once the fight started at the Jamaica Plain school, the Rev. Shaun O. Harrison Sr., 55, "maneuvered himself into a mediator's role between them," said the official, who was not authorized to speak publicly about details of the case.
The official declined to say whether the student shot in the back of the head at 7:15 p.m. Tuesday on Magazine Street was involved in the fight allegedly started by Harrison. The boy survived, despite being shot behind the ear, officials said.
Boston public school spokeswoman Denise Snyder declined to comment on the fight. Harrison's defense lawyer, Kernahan Buck, did not return calls Friday.
Harrison, a Roxbury resident, was fired Thursday after officials learned he was arrested in the shooting case. He is being held on $250,000 bail after pleading not guilty to five charges, including armed assault to murder.
The allegations painted a dark side of Harrison, who made a name for himself as an antigang activist and minister, and came to English High in the newly created role of "dean of academy" Jan. 5.
Prosecutors allege the teen had been selling marijuana for several months at Harrison's behest before they got into a dispute. When they met Tuesday evening, Harrison told the teen they were headed to a house to get marijuana and meet girls, according to Suffolk Assistant District Attorney David Bradley.
During Harrison's arraignment Thursday, Bradley said the student had been in a fight at school before the shooting, but did not provide details.
Surveillance video that prosecutors allege captured the shooting shows a man on a cellphone raise his hand toward the head of a person walking in front of him. The man on the phone then flees.
The student identified Harrison, and told investigators the man he considered a mentor and called "Rev" kept a rifle and shotgun in his Pompeii Street residence, where he also displayed a mural of Latin Kings gang members.
A police cruiser sat in front of the brick apartment building Friday afternoon. Investigators executed a search warrant there, according to the office of Suffolk District Attorney Daniel F. Conley.
Neighbors said they had complained to police about drug activity. "The door never closed," said one resident, who did not want to give his name because of the investigation.
Three others were arrested after police investigating the shooting saw them leave Harrison's apartment Wednesday. Investigators believe Oscar Pena, 19; Wilson Peguero, 23; and Dante Lara, 24, were removing evidence from the residence, Bradley said in court.
Police executing a search warrant after the men's arrest found "more potential evidence," said a law enforcement official briefed on the investigation. All three men face drug charges. Lara and Pena are also accused of firearms offenses.
The Rev. Gregory G. Groover Sr., pastor at Charles Street A.M.E. Church and former chairman of the Boston School Committee, said he was shocked by the allegations against Harrison.
Groover, who led the School Committee from 2009 to 2013, said he did not help Harrison get a job with the School Department. "He never asked for any recommendation," Groover said. "He never asked for any type of assistance."
Harrison began working for the School Department in 2010 as a paraprofessional at the now-closed Odyssey High School in South Boston, Snyder said. When Odyssey closed, the students and staff transferred to Boston Green Academy, where Harrison was a "community field coordinator," Snyder said.
She said he was laid off and then hired in August as a paraprofessional at Orchard Gardens K-8 Pilot School. While he was working at Orchard Gardens, English High advertised a new position, paid for with grant money, to coordinate services for students and families, Snyder said.
Harrison applied and was one of four finalists who interviewed with the school's hiring committee, she said. English High gave the job the title "dean of academy," but Harrison referred to himself as dean of students, Snyder said.
She said none of Harrison's jobs required education licenses or certifications and that he underwent a criminal background check. He holds a bachelor of science degree in human services from Springfield College, a school spokesman said.
For a time, Harrison was also associated with Charles Street A.M.E. Church.
Groover said Harrison worshipped there from 2005 or 2006 until 2012 and was listed on its website as doing street ministry.
Peter Schworm of the Globe staff contributed to this report. Laura Crimaldi can be reached at laura.crimaldi@ globe.com.