HARRISBURG, Pa. (AP) — A 28-year-old criminal justice graduate student was arrested in eastern Pennsylvania on Friday as a suspect in the mysterious stabbing deaths of four University of Idaho students last month, authorities said.

DNA evidence played a key role in identifying Bryan Christopher Kohberger as a suspect in the killings, and officials were able to match his DNA to genetic material recovered during the investigation, a law enforcement official said. The official spoke on condition of anonymity because they were not authorized to publicly discuss details of the ongoing investigation.

The students — Kaylee Goncalves, Madison Mogen, Xana Kernodle and Ethan Chapin — were stabbed to death at a rental home near campus in Moscow, Idaho, sometime in the early morning hours of Nov. 13.

Moscow Police Chief James Fry said Kohberger attends Washington State University, which is only a few miles across the state line from Moscow.

Investigators are still looking for a weapon, Fry said at a press conference. He was emotional as he announced the arrest, calling the victims by their first names.

The killings initially confounded law enforcement and shook the small farming community of about 25,000 people, which hadn’t had a murder for five years. But tips began pouring in after law enforcement asked the public for help finding a white Hyundai Elantra sedan seen near the home around the time of the killings.

In addition to the DNA evidence, authorities also learned Kohberger had a white Hyundai Elantra, the official who spoke anonymously said. In recent days, federal investigators had been watching Kohberger and arrested him early Friday morning at a home in Chestnuthill Township, Pennsylvania.

Federal and state investigators are now combing through his background, financial records and electronic communications as they work to identify a motive and build the case, the official said. The investigators are also interviewing people who knew Kohberger, including those at Washington State University, the official said.

During the press conference, Latah County Prosecutor Bill Thompson said investigators believe Kohberger broke into the students’ home “with the intent to commit murder.” He is being held without bond in Pennsylvania, and will be held without bond in Idaho once he is returned, Thompson said. The affidavit for four charges of first-degree murder in Idaho will remain sealed until he is returned, as required by state law.

Kohberger is also charged with felony burglary in Idaho, Thompson said. An extradition hearing is scheduled for Tuesday.

Kohberger just completed his first semester as a PhD student in the Department of Criminal Justice and Criminology at Washington State University. He is also a teaching assistant for the university’s criminal justice and criminology program, according to WSU’s online directory. University police assisted Idaho law enforcement in executing search warrants at Kohberger’s campus apartment and office, the university said. WSU officials did not immediately respond to a request for comment about Kohberger’s work as a teaching assistant.

“This horrific act has shaken everyone in the Palouse region,” said WSU provost Elizabeth Chilton in a prepared statement, referring to the scenic rolling hills surrounding both universities. “We will long feel the loss of these young people in the Moscow-Pullman community and hope the announcement today will be a step toward healing.”

WSU and UI are partners in several academic programs, and students sometimes attend classes and seminars or work at the neighboring schools. That doesn’t appear to be the case with Kohberger: University of Idaho President Scott Green wrote in a memo to students and employees on Friday evening that the Idaho school had no record of him.

Kohberger graduated from Northampton Community College in Pennsylvania with an associate of arts degree in psychology in 2018, said college spokesperson Mia Rossi-Marino. DeSales University in Pennsylvania said that he received a bachelor’s degree in 2020 and completed graduate studies in June 2022.

Goncalves, 21, of Rathdrum, Idaho; Mogen, 21, of Coeur d’Alene, Idaho; Kernodle, 20, of Post Falls, Idaho; and Chapin, 20, of Conway, Washington, were members of the university’s Greek system and close friends. Mogen, Goncalves and Kernodle lived in the three-story rental home with two other roommates. Kernodle and Chapin were dating and he was visiting the house that night.

Autopsies showed all four were likely asleep when they were attacked. Some had defensive wounds and each was stabbed multiple times. There was no sign of sexual assault, police said.

Police said Thursday the rental home would be cleared of “potential biohazards and other harmful substances” to collect evidence starting Friday morning.

Shanon Gray, an attorney representing Goncalves’s father, Steve Goncalves, said law enforcement officials called the family last night to let them know about the arrest, but gave no additional information about how or why they believe he might be connected to the murders.

Ben Roberts, a graduate student in the criminology and criminal justice department at WSU, described Kohberger as confident and outgoing, but said it seemed like “he was always looking for a way to fit in.”

“I had honestly just pegged him as being super awkward.” Roberts said.

Roberts started the program in August — along with Kohberger, he said — and had several courses with him. He described Kohberger as wanting to appear academic.

“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.”

Ethan Chapin’s family emailed a statement after the press conference. “We are relieved this chapter is over because it provides a form of closure. However, it doesn’t alter the outcome or alleviate the pain,” the family wrote. “We miss Ethan, and our family is forever changed.”

The case enticed online sleuths who speculated about potential suspects and motives. Safety concerns also had the university hiring an additional security firm to escort students across campus and the Idaho State Police sending troopers to help patrol the city’s streets.

Kohberger was arrested in eastern Pennsylvania in the Pocono Mountains. No lawyer for Kohberger was listed in court documents and phone calls to the county public defender’s office went answered Friday.

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Boone reported from Boise, Idaho, and Balsamo reported from Washington. News Researcher Rhonda Shafner in New York, and reporters Mark Scolforo and Brooke Schultz in Harrisburg, Pennsylvania, Michael Kunzelman in Silver Spring, Maryland, and Martha Bellisle in Seattle also contributed.