Two people have been killed in a shooting incident at Virginia Tech University. The two casualties include a police officer.

Law enforcement officers leave the site where a Virginia Tech police officer was shot and killed at Virginia Tech University Blacksburg, Virginia December 8, 2011.

The school didn't confirm the identity of the other. Virginia State police have been requested to take the lead in the investigation. The school is currently locked down, and all transit services have been suspended. The status of the shooter is unknown. Virginia Tech has also asked visitors not to come to campus.

A police officer secures the scene where a gunman killed a police officer and another person after a traffic stop Thursday, Dec. 8, 2011 on the campus of Virginia Tech, in Blacksburg, Va.

The incident brought to mind the April 2007 massacre, when a student killed 32 people and wounded 25 others before committing suicide on the school's rural campus.

It was the worst school shooting in US history.