The shooting at Great Mills High School in Southern Maryland last Tuesday was over in about a minute.

Just before the first class period started, Austin Wyatt Rollins pulled out his father’s handgun in a hallway and fired one shot. It struck his former girlfriend, Jaelynn Willey, in the head and the other student, Desmond Barnes, in the leg. Moments later, Rollins, 17, was dead in another part of the school.

But before Monday, it was not clear whether the gunman had killed himself or whether the resource officer, Deputy Blaine Gaskill, fatally shot him. The St. Mary’s County Sheriff’s Office said its investigation had found that Rollins fired one shot at Willey, 16, and then one more into his head at the same time Gaskill fired his weapon.

Gaskill’s shot missed Rollins but struck his handgun, the Sheriff’s Office said. In its initial report after the shooting, the Sheriff’s Office said Gaskill and Rollins had exchanged gunfire.

Amid the national debate over gun control and school shootings, Gaskill was heralded for his swift response and hailed as an example of how officers on campus can quickly end shootings. In the wake of the deadly school shooting in Parkland, Florida, politicians including President Donald Trump have called for arming teachers and placing additional officers on campuses. Some have criticized those ideas.

After the Maryland shooting, Willey was taken to University of Maryland Prince George’s Hospital Center. Her parents said she was taken off life support Thursday after she had been declared brain dead.

This article originally appeared in The New York Times.

MATTHEW HAAG © 2018 The New York Times