According to multiple reports, two people were injured and one person killed after gunshots erupted at a Maryland high school on Tuesday morning.

Great Mills High School was on lockdown after one student shot a 16-year old female student, also hitting a 14-year old male student right before classes started around 8 a.m. ET. The shooter was killed by a school resource officer, according to NBC News.

Law enforcement officials said that the shooter was taken to a hospital and later died from his injuries.

St. Mary’s County Sheriff Tim Cameron told NBC Washington that the shooting was “contained.”

Cameron said the officer shot “at least a round at the shooter, and I believe the shooter also fired a round.”

The female victim is listed in critical condition, and the male victim is in “good condition,” reps for MedStar St. Mary’s Hospital told NBC.

All St. Mary’s County high schools have armed deputy sheriff’s who act as school resource officers, per reports.

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

Great Mills students participated in the National School Walkout last Wednesday to honor the victims of the Parkland, Florida school shooting that left 17 people dead on Feb. 14.

The latest school shooting comes just days before Saturday’s student-led March For Our Lives rally to call attention to gun violence.