A Maryland high school was briefly placed on lockdown Monday after authorities say a school resource officer fatally shot himself inside his office.

Baltimore County police spokeswoman Officer Jen Peach said at a news conference Monday that police and medics were called to Eastern Technical High School around 12:23 p.m. Peach said surveillance video showed the officer walking alone into his office in the school's basement. Faculty members heard a gunshot and responded.

Peach identified the officer as J. Comegna, a 21-year veteran of the department who died at a hospital after suffering an upper-body wound.

County school officials tweeted that students and staff were safe and sheltering in place. All afternoon and evening activities were canceled. Students were dismissed at their usual time and classes were expected to be held as scheduled on Tuesday.