St Mary’s County sheriff’s spokeswoman Cpl Julie Yingling said there are injuries at Great Mills High School but she did not know how many or the severity of the injuries.
She also said she had no information about fatalities.
Agents from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives were heading to the scene.
The county sheriff said deputies are on the scene and that parents or guardians should stay away, going instead to Leonardtown High School to reunite with Great Mills students there.
Maryland governor Larry Hogan and Representative Steny Hoyer tweeted that they are monitoring reports and urged people to follow the instructions of local law enforcement at the scene.
More to follow....