GREAT MILLS, Md. (WJLA) – At least three students were reportedly injured – including the shooter – Tuesday morning in a shooting at a high school in St. Mary’s County, Maryland, according to authorities.

The St. Mary’s County Sheriff’s Office says it happened at Great Mills High School and that police are on the scene. ABC7’s Brad Bell said sources tell him the shooter was a student and is one of the three injured. Bell says a school resource officer took action to end the threat and authorities confirmed the incident has been contained.

The shooter targeted girl and then shot a second student. That’s when the school resource officer engaged him.

According to Hot Air:

The sheriff’s PIO told NBC that the incident involved a single male shooter who was a student at the school, who targeted a female student. The armed guard (school resource officer) at the school then engaged in a firefight with the shooter, critically wounding him, and a third student was injured. The shooter and intended target are both critically injured, and the third student is in critical but stable condition. So far, they are not releasing any information on the weapon itself.

Update: This points out the value of having armed resource officers on campus, at least when they are willing to respond. As the PIO pointed out, this could have been a lot worse, especially because the shooting took place in a crowded corridor.