— Police are trying to determine why a 22-year-old part-time Radford University student fatally shot a police officer on the campus of nearby Virginia Tech on Thursday afternoon, and then turned the gun on himself.

The gunman, identified by police late Friday as Ross Truett Ashley, of Spotsylvania County, had no apparent connection to Tech Police Officer Deriek W. Crouse, 39, who was slain as he sat in his cruiser, police said. A day earlier, authorities said, Ashley is suspected of walking into a real estate office in Radford with a gun, demanding car keys and stealing a white Mercedes SUV. That car was found Thursday on Virginia Tech’s campus.

Radford University officials said in a statement that Ashley was enrolled part-time as a business management major, but declined further comment.

Exactly what led to the string of violence remains unclear, but police have said they think Ashley acted alone. They are working to piece together his movements in the hours before the shooting, which occurred just after noon Thursday in the university’s coli­seum parking lot. Crouse had just pulled over a driver in an unrelated incident.

Police said Ashley, dressed in a maroon hoodie and gray hat, walked up to Crouse’s cruiser and opened fire. Crouse, who also is an Army reservist who served in Iraq, left a wife and five children and step-children.

“Motive is very much a fundamental part of this investigation,” said Corinne Geller, a spokeswoman for the Virginia State police.

Ashley appears to have graduated from Spotsylvania High School in 2007 and was a running back on the football team. He won numerous academic awards, according to published reports at that time.

He also appears to have started his academic career at the University of Virginia’s Wise County campus, where he made dean’s list in 2008, according to online records.

“He was a good kid,” said Barry Perry, who knew Ashley when he was an athlete at Spotsylvania High. “An average kid. Somebody that seemed to be a good member of the community.”

Perry said “I can’t believe he’d be involved in anything like that.” He called Ashley “a heck of an athlete . . .good player”

At a news conference Friday morning, authorities offered a fresh account of the chaotic events that brought the campus to a standstill for several hours and grabbed national headlines.

Around 12:15 p.m. Thursday, Crouse was on patrol in the stadium parking lot, when he pulled over a Tech student, Geller said. As Crouse sat in his vehicle, Geller said the suspect approached and shot him. Crouse was not able to return fire, but the suspect’s image was captured by a dashboard video camera in his car.

Ross Truett Ashley. (AP)

The shooter then ran. Police said the student that Crouse had pulled over has no connection to the shooter and has been helpful during the investigation.

Next, the shooter ran to a set of nearby greenhouses, where he changed his clothes, Geller said. He left behind a pullover and a wool cap stashed in a backpack, which police later discovered.

Around 12:45 p.m., a Montgomery County Sheriff’s deputy, spotted the suspect in the back of an enclosed campus parking lot, known as “The Cage,” which is about a half-mile from where Crouse was shot, Geller said. The suspect was acting furtively and a bit strangely, she said.

The deputy briefly lost track of the shooter, but found him again sprawled on the ground with a handgun nearby, Geller said, and he appeared to have shot himself. Police said ballistics evidence tied the gun to both shootings.

Geller said it took police several hours to declare the campus safe because they wanted to be sure they had the shooter, since the man found in the parking lot was wearing different clothes than the ones witnesses said they saw the man wearing at the scene of Crouse’s shooting.

“We wanted to make sure and confirm absolutely that we were dealing with the exact same individual,” Geller said.

Nadean Gilbert, whose son James Gilbert owns Gilbert Real Estate, where the robbery of the SUV occurred, said Ashley walked into the office Wednesday and calmly asked the office manager for her car keys.

“She said, ‘What do you want my keys for?’ ” Gilbert said.

“Then he put a gun up.”

They were shocked, she said. “They said he was a very clean-cut man. One of the girls said she thought she recognized him. But they didn’t think they knew him,” she said.

The Thursday shooting created a sense of déjà vu for a campus still healing from the 2007 massacre, in which a disturbed student fatally shot 32 people and himself. Students gathered for vigils again. They lit candles once more and were grappling with the same unanswerable questions.

“People are always like, ‘Virginia Tech is the safest place because nothing like 2007 could ever happen again,’ ” said Erika Koenig, 18, a freshman from Severn. “You have to wonder: Why us?”

The spotlight on the violence has not hurt the university’s reputation, said Lawrence G. Hincker, associate vice president for university relations. Since 2007, he said the school has seen increases in the number of applications and high-profile students who enroll, and philanthropic giving.

The focus of the mourning has become the “April 16 Memorial” for the victims slain in 2007 by Seung Hui Cho, a disturbed English major from Fairfax County. Hundreds attended vigils at the site on Thursday and Friday nights. The events were a chance to remember and showcase the community’s resiliency.

On Thursday, students silently lit candles, cried and prayed at the site. Then, student Chris Mundy, one of the students and supporters who have sprung into action, organizing vigils and helping raise more than $18,000 for Crouse’s family, made his way to the front of the group. The orange and maroon Hokies’ colors were all around.

Mundy gave a short speech and yelled: “Let’s Go!”

The crowd answered: “Hokies!”

The cheer resounded across the drill field adjacent to the memorial, which is a semi-circle with a stone for each victim. Kevin Burke, 21, a senior from Leesburg, spoke next.

“The fact that this has happened twice is unfathomable,” Burke said of the shooting tragedies on the campus. “The fact that we are still paying our respects is awesome.”

The same spirit showed up online, too. Some students changed their Facebook profile pictures to a black ribbon overlaying the Virginia Tech badge. Others chose a photo of a Thursday evening sunset over campus. The message: God is watching over us.

“There’s a status on Facebook that many are posting about Virginia Tech,” said Sara Seeba, 18, a freshman from Salisbury, Md. “‘From the outside looking in, you can never understand it. From the inside looking out, you can never explain it. Blacksburg is our home. This is our family.’”

Her voice cracked with emotion.

In one instance, Virginia Tech’s twin tragedies touched the same family. Kevin Myers, 21, a senior from Ashburn, said his sister, Jessica, lived through Cho’s rampage, while she was a student at Tech. She lost a sorority sister on April 16, 2007.

Kevin Myers said she frantically called and texted him all day Thursday to make sure he was safe and coping emotionally. He said she helped bring him through the horrible events.“My sister was the one who knew what we were going through,” Kevin Myers said.

Staff writers Jenna Johnson Anita Kumar, Susan Svrluga and Marty Weil in Washington and researchers Jennifer Jenkins and Julie Tate contributed to this report.