BLACKSBURG, Va. (AP) - The young man who killed a Virginia Tech police officer walked up to the patrolman he did not know and fired, then took off for the campus greenhouses, ditching his pullover, wool cap and backpack. He made his way to a nearby parking lot and when a deputy spotted him, he took his own life, leaving fresh questions on a campus still coping with the nation's worst mass slaying in recent memory.
Why didn't he run or engage the deputy who closed in? Was he even aware thousands of students had just been alerted by cell phone that a gunman was on the loose and the campus was locked down? And why did he shoot an officer at a school he never attended?
"That's very much the fundamental part of the investigation right now," state police spokeswoman Corrine Geller said Friday at a news conference.
Authorities said they know who the gunman is, but they were waiting to publicly name him because they said his family didn't know yet. A law enforcement official who spoke on condition of anonymity described the shooter as in his early 20s from Virginia.
The gunman was likely the same young man who is accused of stealing a 2011 white Mercedes SUV from a real estate office Wednesday in Radford, which is about 15 miles from Virginia Tech. Office employees told police a man came in with a handgun and demanded keys to one of their vehicles.
The office is located in a gritty part of Radford and caters to students who go to the city's small namesake school. At the real estate office Friday, the shades were drawn and the doors locked.
It's not clear what happened between the robbery and 24 hours later when university officer Deriek W. Crouse, 39, was shot. Police were looking for surveillance video around campus to see if it would lend any clues to the gunman's whereabouts before the shooting.
Crouse was a trained firearms and defense instructor with a specialty in crisis intervention. He had been on the force for four years, joining about six months after 33 people were killed in a classroom building and dorm April 16, 2007.
At 12:15 p.m. Thursday, Crouse pulled over a student and was shot while sitting in his unmarked cruiser. The student didn't have any link to the gunman, Geller said.
Shortly before 12:30 p.m., police received a call from a witness who said an officer had been shot. About six minutes later, the first campus-wide alert was sent by email, text message and electronic signs in university buildings. Many students on campus were preparing for exams, and some described a frantic scene after the initial alert. Soon, heavily armed officers were walking around campus, caravans of SWAT vehicles were driving around and other police cars with emergency lights flashing patrolled nearby.
Students outdoors went inside buildings. Those already there stayed 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 he left some of his clothes and his ID.
Fifteen minutes after the witness called police, a deputy sheriff on patrol noticed a man at the back of another parking lot about 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 Cage parking lot and lost sight of the man for a moment. The deputy then found the man lying on the pavement, shot to death. The handgun was nearby.
Police said nobody witnessed the suicide, the parking lot apparently vacant because of warnings. For three more hours, students checked their phones, computers and TVs. Finally, the school gave the all clear.
The events unfolded on the same day Virginia Tech officials were in Washington, fighting a federal government fine over their handling of the 2007 massacre, and the shooting brought back painful memories. About 150 students gathered silently Thursday night for a candlelight vigil on a field facing the stone plaza memorial for the 2007 victims.
"Why Tech, why again?" said Philip Sturgill, a jewelry store owner. "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 worked exactly as expected.
"It's fair to say that life is very different at college campuses today. The telecommunications technology and protocols that we have available to us, that we now have in place, didn't exist years ago," he said. "We believe the system worked very well."