Authorities in Blacksburg, Virginia say a gunman has shot and killed a police officer who was conducting a traffic stop at Virginia Tech, the site of a mass shooting in April 2007.

Officials say that during Thursday's stop, the gunman walked up to the officer and opened fire, killing him. But investigators say that at this time and based on initial reports, they do not believe the gunman was in any way related to the traffic stop at the university.

They also say that a short time later, the body of a second person was discovered on the campus. Officials did not say whether the second deceased person was the gunman who killed the officer.

The school issued a campus-wide alert calling on people to stay indoors and advising visitors to stay away from the campus. The alert was later lifted.

Virginia Governor Bob McDonnell issued a statement saying he was deeply saddened by news of another tragedy affecting the Virginia Tech community. He said his thoughts and prayers are with the families of those affected by these shootings.

Republican House Majority Leader Eric Cantor also spoke about the incident while on the floor of the House of Representatives. Cantor said lawmakers again express their sorrow to those mourning the loss of life and extend their thoughts to the school's president, Charles Steger, and to that community.

School officials say final exams scheduled for Friday have been postponed.

On April 16, 2007, a Virginia Tech student, Seung-Hui Cho, killed 32 people on the campus before committing suicide.

Thursday's incident came as officials from the school were in Washington to appeal a $55,000 fine by the U.S. Department of Education in connection with the university's response to the 2007 rampage.

The school was criticized for a two-hour delay in alerting students after Cho shot his first two victims in a dormitory. The rampage was the deadliest mass shooting in modern U.S. history.