A gunman has opened fire inside a US school with reports of several people shot.
The shooting has taken place at Great Mills High School in Lexington Park, Maryland.
Several students have been reported to have been shot when an active shooter came to the school.
A mass casualty incident has been declared.
Great Mills High School was put on lockdown following the shooting, school officials confirmed.
Maryland State Police also told Fox News they were responding to the incident.
Police are asking parents to stay away from the school but the incident has been contained.