(AP) - Police identified the Virginia Tech gunman on Friday as a part-time college student from nearby Radford University, though they still have not been able to say what led him to kill a police officer and then himself.

The day before Thursday's shooting and campus-wide lockdown,Ross Truett Ashley, 22, stole a sport utility vehicle at gunpointfrom a real estate office in Radford, police said. He dumped thecar on the Virginia Tech campus and it was found Thursday.

Police said that same day he walked up to the patrolman he didnot know and fired, then took off for the campus greenhouses,ditching his pullover, wool cap and backpack. He made his way to anearby parking lot and when a deputy spotted him, he took his ownlife, leaving fresh questions on a campus still coping with thenation's worst mass slaying in recent memory.

Why didn't he run or engage the deputy who closed in? Was heeven aware that thousands of students had just been alerted by cellphone that a gunman was on the loose and the campus was lockeddown? And why did he shoot an officer at a school he neverattended?

"That's very much the fundamental part of the investigationright now," state police spokeswoman Corrine Geller said Friday ata news conference.

Deriek W. Crouse, 39, was the slain officer. Crouse was atrained firearms and defense instructor with a specialty in crisisintervention. He had been on the force for four years, joiningabout six months after 33 people were killed in a classroombuilding and dorm April 16, 2007.

At 12:15 p.m. Thursday, Crouse pulled over a student and wasshot while sitting in his unmarked cruiser. The student didn't haveany link to the gunman, Geller said.

Shortly before 12:30 p.m., police received a call from a witnesswho said an officer had been shot. About six minutes later, thefirst campus-wide alert was sent by email, text message andelectronic signs in university buildings. Many students on campuswere preparing for exams, and some described a frantic scene afterthe initial alert. Soon, heavily armed officers were walking aroundcampus, caravans of SWAT vehicles were driving around and otherpolice cars with emergency lights flashing patrolled nearby. Students outdoors went inside buildings. Those already therestayed put. Everybody waited.

Police aren't sure what the gunman was doing at this point.After the shooting, he fled on foot to the greenhouses, where heleft some of his clothes and his ID.

Fifteen minutes after the witness called police, a deputysheriff on patrol noticed a man at the back of another parking lotabout a half-mile from the shooting. The man was by himself,looking around furtively and acting "a little suspicious,"according to Geller.

The deputy drove up and down the rows of the sprawling Cageparking lot and lost sight of the man for a moment. The deputy thenfound the man lying on the pavement, shot to death. The handgun wasnearby.

Police said nobody witnessed the suicide, the parking lotapparently vacant because of warnings. For three more hours,students checked their phones, computers and TVs. Finally, theschool gave the all clear.

The events unfolded on the same day Virginia Tech officials werein Washington, fighting a federal government fine over theirhandling of the 2007 massacre, and the shooting brought backpainful memories. About 150 students gathered silently Thursdaynight for a candlelight vigil on a field facing the stone plazamemorial for the 2007 victims.

"Why Tech, why again?" said Philip Sturgill, a jewelry storeowner. "It's so senseless. This is a lovely, lovely place."

An official vigil is planned Friday night.

School spokesman Larry Hincker said the alert system workedexactly as expected.

"It's fair to say that life is very different at collegecampuses today. The telecommunications technology and protocolsthat we have available to us, that we now have in place, didn'texist years ago," he said. "We believe the system worked verywell."