Authorities in Blacksburg, Virginia say a gunman has shot and killed a police officer who was conducting a traffic stop at Virginia Tech University, 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.

They also say that a short time later, the body of a second person was discovered on the campus. Officials will 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 single gunman killed 32 people on the campus before committing suicide.

Earlier this year, federal officials fined the school, formally known as Virginia Polytechnic Institute and State University, for waiting too long to notify staff and students during the 2007 rampage, which was the deadliest mass shooting in modern U.S. history.