IDAHO — A criminology graduate has been arrested in the mysterious killings of four university students in the state of Idaho last month, police say.

Bryan Christopher Kohberger, 28, was detained in Pennsylvania, over 2,500 miles (4,020km) from the crime scene.

The University of Idaho students were found stabbed to death in their beds in a rental home near the campus on Nov. 13.

Police say the suspect lived in a town near where the murders occurred.

Xana Kernodle, Ethan Chapin, Kaylee Goncalves and Madison Mogen were discovered dead from multiple stab wounds in the home in the small college city of Moscow, northern Idaho.

Some of the students, who were all 20 or 21 years old, had defensive injuries.

A post-mortem examination found the four were probably asleep when they were attacked. There was no evidence of sexual assault, police said.

Kohberger was arrested near the city of Scranton, Pennsylvania, on Friday by state police and FBI agents. He was traced to his parents’ home in Albrightsville, officials told CBS, the BBC’s US partner.

Latah County prosecutor Bill Thompson told a news conference the accused faces four counts of first-degree murder and felony burglary.

The suspect, who is expected to be extradited to Idaho, has already appeared before a judge, and was remanded in custody without bail.

Officials confirmed at the same news conference that the suspect was a PhD student in criminal justice and criminology at Washington State University.

Its campus in the town of Pullman, Washington — where the suspect was living — is a 10-mile drive across the border to Moscow.

“This was a complex and extensive case,” said an emotional Moscow police chief James Fry.

“These murders have shaken this community and no arrest will ever bring back these young students,” he told reporters.

Police did not disclose any motive, saying it was necessary to keep certain details private in order to secure a conviction at trial. They said they were investigating whether the suspect knew the victims.

Chief Fry said they had so far reviewed more than 19,000 tips from the public.

Earlier this month, investigators’ big break may have come after they asked the public for help finding a white Hyundai Elantra car seen near the victims’ home on the day of the murders.

Police said on Friday an Elantra had been recovered, but the murder weapon has yet to be found.

The police chief refused to comment about reports that the suspect asked officers if anyone else had been arrested.

“What I can tell you is we have an individual in custody who committed these horrible crimes and I do believe our community is safe,” he said. “But we still need to be vigilant, right?”

Unnamed law enforcement officials told US media that DNA evidence links Kohberger to the crimes.

He is listed as an assistant instructor for three undergraduate criminal courses at Washington State University, according to the Idaho Statesman.

Until now he had no known arrest record in Idaho, Washington or Pennsylvania, the newspaper reports, adding that he had been cited by police for not wearing a seatbelt last August in the Idaho county that includes Moscow.

A fellow graduate student in his program told the Associated Press news agency that the suspect had appeared confident and outgoing, but also “super awkward”.

Ben Roberts added that Kohberger had wanted to appear clever.

“One thing he would always do, almost without fail, was find the most complicated way to explain something,” he said. “He had to make sure you knew that he knew it.”

Family members of the victims had voiced frustration with the investigation’s progress.

The arrest came on the same day a memorial service was held for Goncalves and Mogen at a church in Coeur D’Alene, Idaho.

“Today we are commemorating our Maddie’s and her friend Kaylee with relief knowing that she can now be properly laid to rest,” said a statement from Mogen’s family.

A statement from the family of Ethan Chapin to US media said they were “relieved this chapter is over because it provides a form of closure”.

“However, it doesn’t alter the outcome or alleviate the pain. We miss Ethan, and our family is forever changed.” — BBC