It's another prime example of how a good guy with a gun can save dozens of innocent lives when under attack by a madman hellbent on mass murder.

A student gunman at Great Mills High School in Southern Maryland tore through the campus at 8 a.m. Tuesday, shooting and injuring two students.

"There was a loud sound and everyone started screaming and running," tweeted student Mollie Davis.

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But an armed school resource officer, Blaine Gaskill, wasn't about to stand down or wait for backup.

He was determined to save innocent young lives. So Gaskill wasted no time in pursuing attacker Austin Wyatt Rollins, 17, who was armed with a Glock handgun.

Gaskill fired a round at the gunman and quickly neutralized the threat.

Nobody was killed, except for Rollins.

Two injured students – a 14-year-old boy and 16-year-old girl – are receiving treatment at local hospitals. The boy is in stable condition at MedStar St. Mary Hospital. The girl is critical at the University of Maryland Prince George's Hospital Center. Gaskill was not injured.

It's a stark contrast to the Valentine's Day shooting five weeks ago at Marjory Stoneman Douglas High School in Parkland, Florida, where 17 people were killed. In that case, the school resource officer waited outside the school as the gunman massacred students inside.

During his Tuesday show, talk-radio host Rush Limbaugh declared: "If the media could do one thing right here ... they would make damn certain the world knows how he was stopped. It wasn't a gun-free zone. ... It was nothing more than an armed security agent ... and this worked.

"Thank God for the armed security. ... What definitely needs to be publicized is how this was stopped."

Earlier Tuesday, Limbaugh had urged the media to refrain from publishing Rollins' name. He said refusing to give publicity to the attacker might help prevent future shootings.

Sheriff Tim Cameron said Gaskill fired "at least a round at the shooter, and I believe the shooter also fired a round."

He added: "This is what we train for. This is what we prepare for and this is what we pray we never have to do. And on this day we realized our worst nightmare that our greatest asset – our children – were attacked in a bastion of safety and security, one of our schools."

Meanwhile, the Florida school shooting has triggered a wave of anti-gun activism among students there. Students across the country participated in a "school walkout" last Wednesday. They also plan to attend a march in Washington, D.C., this weekend called "March for Our Lives."

David Hogg, a 17-year-old senior at Marjory Stoneman Douglas High School has become a leader of the "Never Again" movement for gun control. Hogg has said proposals to arm teachers, which are advocated by President Trump, are "disgusting."

Limbaugh said the Maryland school situation "ended well for a specific reason." That's because a "good guy with a gun" acted quickly and saved innocent lives.

"If David Hogg had his way, there wouldn't be any armed security in the schools," he said. "David Hogg and all the students at Parkland, if they had their way ... this shooting in Maryland would have gone on a lot longer."

In a statement posted to Twitter after Tuesday's shooting, Maryland Gov. Larry Hogan said "prayers are not enough" when it comes to preventing 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. "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."