Last Wednesday, hundreds of students at Great Mills High School in Maryland walked out of class to protest gun violence. Less than a week later, they were left reeling from a shooting on their own campus.

On Tuesday, two Great Mills students—a 16-year-old female and a 14-year-old male—were injured when a student, identified by police as 17-year-old Austin Wyatt Rollins, opened fire with a handgun in a hallway, according to NBC News. The female victim is in critical condition, while the male is in stable condition, the outlet reported.

A school resource officer exchanged shots with Rollins, who died after being taken to the hospital, according to St. Mary’s County Sheriff Tim Cameron. The resource officer, who was trained and armed, was not injured.

“There is an indication that a prior relationship existed between the shooter and the female victim,” Cameron said at a press conference.

An active shooter was reported on school grounds around 8 a.m., according to police. Agents from the Federal Bureau of Investigation and the Bureau of Alcohol, Tobacco, Firearms and Explosives were on the scene, according to the Associated Press. Great Mills High School is less than 70 miles away from Washington, D.C.

"You train to respond to this and you hope that you never ever have to," Cameron said. "This is the realization of your worst nightmare—that, in a school, that our children could be attacked.”

The shooting comes just six days after at least 250 Great Mills students participated in the National School Walkout, joining thousands of other teenagers across the country to protest gun violence, SoMdNews reported.

“We always thought that it would never happen at our school, in our small town,” Great Mills senior Natalie Perez, 17, told The Daily Beast in a message via Twitter on Tuesday. “We were protesting for the lives of other students who were affected by gun violence, never realizing that we were also protesting for our own lives.”

Students walked out of class for 17 minutes, in honor of the 17 victims of last month’s school shooting in Parkland, Florida.

“I’m encouraged that our kids are stepping up to the plate and I support our kids,” Principal Jake Heibel said, according to The Bay Net.

The Maryland shooting follows an uprising of student activists who’ve called for gun control after the violence in Parkland.

Mason Stoneman Douglas High School students have taken to social media and the streets, pressing their elected officials to enact legislation after the deadly massacre. Florida Gov. Rick Scott recently signed a bill that banned bump stocks and raised the minimum age to buy a gun to 21, breaking from the state’s conservative-leaning gun laws. The Parkland school shooting survivors have also planned March for Our Lives, a larger anti-gun violence rally that will take place on Saturday in the nation’s capital and other major cities.

"Less than a WEEK ago Great Mills High School students walked out with us to protest gun violence...now they’re experiencing it for themselves," Florida school shooting survivor Jaclyn Corin tweeted Tuesday. "The state of our country is disgusting—I’m so sorry, Great Mills."

On Tuesday, students weren’t initially alarmed when their principal asked everyone to clear the hallways.

Perez, 17, told The Daily Beast students were “talking and laughing, joking how this was similar to freshman year when we had a lockdown for a false bomb threat.”

Moments later, the principal called for a lockdown and some classmates hid in the bathroom.

Perez says she heard police yelling down the hallway, and students started to realize “it wasn’t a fake bomb threat, but rather a very real school shooting.”

“Police officers came into the back room with guns,” Perez told The Daily Beast in a message via Twitter. “And told us that we needed to go very quickly down to the cafeteria and keep our hands up.”

“My main thought was, ‘I’m not sure what’s going to happen, but I need to tell all of my friends and family that I love them,’” she added.