Update A Maryland high school student who shot two classmates with a handgun this morning has died, local law enforcement officials have confirmed. The two other students remain in critical condition.

According to the St. Mary’s County Sheriff’s Department, a school resource officer responded to the hallway shooting by firing a round at the shooter. Sheriff Tim Cameron said at a press conference that it had not been determined whether the gunman died from the officer’s bullet or from a self-inflicted wound.

The identities of the shooter and his victims were not disclosed. The sheriff would not confirm reports that the shooter had targeted the female student, setting off the incident.

The event at the school was described as “contained” by the school district earlier this morning. The shooting began before classes started at 8 am.

Parents and guardians were being directed to another school – Leonardtown High School – for “reunification” with Great Mills students.

The shooting comes just four days before Saturday’s March for Our Lives rally in Washington DC and thousands of smaller marches and rallies across the country. The march will be the latest protest against gun violence in the wake of the Marjory Stoneman Douglas High School in Parkland, Florida. Earlier this month, hundreds of thousands of the nation’s students left classrooms as part of the National School Walkout, with a protest rally outside the White House held the same day (see photo above).