During about a one-hour period on Thursday, the university issued four separate alerts.
Derek O'Dell, a third-year veterinary student at Virginia Tech who was wounded in the 2007 shooting, was shaken.
"It just brings up a lot of bad feelings, bad memories," said O'Dell, who was at his home a couple of miles from campus at the time of the shootings.
"At first I was just hoping it was a false alarm," he said. "Then there were reports of two people dead, and the second person shot was in the parking lot where I usually park to go to school, so it was kind of surreal."
On Thursday night, about 150 students gathered silently for a candlelight vigil on a field facing the stone plaza memorial for the victims of the 2007 massacre. Though the official vigil was moved to Friday evening, many turned out anyway to show their support. One student came forward to invite everyone back a day later. He shouted, "Let's go!" The crowd responded, "Hokies!"
Police would not rule out a connection between the shootings and an armed robbery Wednesday in Radford, about 10 miles from Blacksburg. According to media reports, Radford police were looking for a man they considered armed and dangerous after an armed robbery at a local real estate office.
In August, a report of a possible gunman at Virginia Tech set off the longest, most extensive lockdown and search on campus since 2007. No gunman was found, and the school gave the all-clear about five hours after sirens began wailing and students and staff members started receiving warnings.
The system was also put to the test in 2008, when an exploding nail gun cartridge was mistaken for gunfire. Only one dorm was locked down during that emergency, and it reopened two hours later.