Austin Wyatt Rollins, 17-year-old male student shot two other students at Great Mills High School in Maryland on Tuesday morning before a school resource officer engaged him and stopped the threat, according to St. Mary’s County Sheriff Tim Cameron.

The incident began in a school hallway at 7:55 a.m., just before classes started.St. Mary’s County Sheriff Tim Cameron told the local station News 4 that the gunman entered the high school in Great Mills, Maryland, at the start of the school day. He shot a female student in the hallway, and a male student was also hit by a bullet. The shooter exchanged fire with a school resource officer — a trained, armed deputy sheriff — and was wounded. The officer wasn’t.

Blaine Gaskill, an armed campus guard, exchanged gunfire with the attacker.Officials didn’t confirm whether Gaskill hit the attacker, who was pronounced dead at and has not been identified, or whether he took his own life. But if Gaskill’s shot stopped him, the deputy would be only second resource officer to gun down an active school shooter since the Columbine High School massacre in 1999, according to a year-long Washington Post analysis of dozens of school shootings.

Blaine Gaskill was a well-trained and armed sheriff’s deputy who confronted Rollins , potentially preventing additional tragedy.

“This is a tough guy who closed in quickly,” authorities said at the news conference, adding that Gaskill is a SWAT team officer. “He may have saved other lives.” Maryland Gov. Larry Hogan said.

In a statement after Tuesday’s shooting, Hogan warned that “prayers are not enough” when it comes to preventing future school shootings.

“The First Lady and I are praying for those who were injured, their families and loved ones, and for the entire Great Mills community as they come together to heal in the wake of this horrific situation,” Hogan said in a statement. “But prayers are not enough. Although our pain remains fresh and the facts remain uncertain, today’s horrible events should not be an excuse to pause our conversation about school safety. Instead, it must serve as a call to action.”

The two injured students are in critical condition, and the shooter died. The incident occurred just days after students from across the country, including at Great Mills High School, participated in National School Walkout Day to call for gun control and honor the lives of the 17 people killed at Marjory Stoneman Douglas High School in Parkland, Florida, on February 14.