Update: Mayor Marty Walsh announced on Monday a comprehensive internal inquiry of the employment history of Shaun Harrison Sr. is being carried out by the Boston Public Schools labor relations department. The inquiry will consist of interviews with school leaders and other staff members where Harrison worked.

Earlier: The sister of accused Boston English High School dean of students Shaun O. Harrison Sr., who faces charges that he tried to murder one of the school’s students Tuesday night, says the allegations against her brother don’t add up.

“My brother is a good man and I don’t know how this happened,” Susan Harrison told the Boston Globe. “It was a setup.”

Susan’s brother, Shaun, is a 55-year-old veteran of the Boston public school system; a minister and community activist who was arrested Wednesday, following an investigation into a shooting police responded to shortly after 7 p.m. the night before.

Police say officers arrived at 100 Magazine Street, in Roxbury, at 7:13 p.m. Tuesday night. There, officers found a man in his late teens suffering from a gunshot wound. The victim was taken to and treated at Boston Medical Center for non-life-threatening injuries.

Susan Harrison told the Globe she hasn’t been able to speak with her brother since the arrest.

Without identifying the accused dean of students by name, interim BPS superintendent John McDonough said in a statement to the Globe that Harrison Sr. had been fired:

Nothing is more important than the safety and well-being of our students. English High School is filled with committed and caring educators who go above and beyond for their students every day. This school community is strong and its students and teachers have my unwavering support. We are taking appropriate steps to support students and to keep a focus on teaching and learning.

Harrison Sr. has worked at multiple BPS schools since September 2010. On January 5, 2015, he was assigned to a managerial position at English High; Denise Snyder, a BPS spokesperson told the Globe, “at English High School, Mr. Harrison was recognized as their Dean of Students.”

Due to the ongoing nature of the investigation, BPS is not providing any details regarding the dean’s relationship with the student whom he allegedly tried to kill.

Harrison Sr. is a resident of Dorchester. As a minister, he has worked with Boston police in the past to help strengthen the department’s ties to Dorchester and Roxbury, the Globe reports.

Harrison Sr. is due in Roxbury Municipal court Thursday for his arraignment on charges of assault with intent to murder, aggravated assault and battery, and unlawful possession of a firearm, Suffolk District Attorney Dan Conley’s office said.