BLACKSBURG, Va. >> A dean’s list student who killed a Virginia Tech police officer had no ties to the university and did not know the patrolman, authorities said Friday without offering a motive for a crime spree that spanned two days and ended in suicide.

Ross Truett Ashley, 22, first drew authorities’ attention when he robbed his landlord’s office at gunpoint Wednesday. He took the keys to a Mercedes-Benz sport utility vehicle later found in Blacksburg, home to Virginia Tech, about 10 miles away.

Ashley, a part-time business student at Radford University, was described by those who knew him as a typical college student, though he could be quiet and standoffish. He liked to run down the hallways and recently shaved his head, a neighbor said.

Police said he walked up to officer Deriek W. Crouse on Thursday and shot him to death as the patrolman sat in his unmarked cruiser in the midst of a traffic stop. Ashley was not involved in the stop and did not know the driver, police said.

Ashley then took off for the campus greenhouses, ditching his pullover, wool cap and backpack as police sent out a campus-wide alert that a gunman was on the loose, terrorizing students on a campus still coping with the nation’s worst mass slaying in recent memory.

A deputy sheriff on patrol noticed a man acting suspicious in a parking lot about a half-mile from the shooting. The deputy drove up and down the rows of the sprawling Cage parking lot and lost sight of the man for a moment, then found Ashley shot to death on the pavement.

Ashley lived in an apartment on top floor of a gray, three-story brick building that looked a little beaten up on the outside.

On Friday night, students popped in and out of the building visiting friends. Mandy Adams, a Radford grad student, said had Ashley had recently shaved his head. Other than running down the hallways, he was quiet, she said.

"He would just run down the hallway, never walk, always run," said Adams, who was out on a rear fire escape with a glass of white wine and a cigarette to calm her nerves. "It’s going to be really creepy when they come to take his stuff out of here."

Ashley’s apartment was above a yogurt shop, consignment store, barber shop and a tattoo parlor. It overlooked the business section of Radford’s main drag.

Neighbor Nan Forbes, a Radford senior, said he was rarely seen or heard from. She said she knew he was in trouble when she saw two police officers guarding the door to Ashley’s apartment

"It does freak us out because we live in this building, but there was not one peep of trouble, nothing unusual," she said.

Ashley made the dean’s list in 2008 at the University of Virginia-Wise, which is located in southwest Virginia. Officials at Radford or UVA-Wise were not immediately able to talk in detail about Ashley.

At the Virginia Tech campus, thousands of people silently filled the Drillfield for a candlelight vigil Friday night to remember Crouse, a firearms and defense instructor with a specialty in crisis intervention. He had been on the force for four years, joining about six months after a student gunman killed 32 and himself on April 16, 2007.

The vigil included a moment of silence and later closed with two trumpeters stationed across the field from each other playing "Echo Taps" as students raised their candles.

"Let’s go!" one student then shouted. "Hokies!" everyone else responded.

Kathleen O’Dwyer, a fifth-year engineering majors, said it was important to come for Crouse’s family.

"Also it’s for the community, to see the violence that happens isn’t what we’re about," said O’Dwyer, who will be graduating next week.

Her plans when she leaves school?

"First, go home and hug my mom," O’Dwyer said.

Nobody answered the door at Ashley’s parents’ home in Spotsylvania County in the northern part of the state. The house was dark and no vehicles were in the driveway. The two-story, log cabin-style home in a semi-rural area sits about 200 yards off the road up a narrow gravel drive.

Billie Jo Phillippe, who lives three houses down, said she didn’t really associate with the family.

"They stay off to themselves a lot," she said. "He was a clean-cut young guy but standoffish."