Police identified Bryan Christopher Kohberger as the suspect accused of murdering four University of Idaho students in November through DNA using public genealogy databases, law enforcement sources told ABC News.
Local police and the FBI tracked him to Pennsylvania through his vehicle. The FBI surveilled the house in the Pocono Mountains for four days prior to the arrest.
The 28-year-old was arrested Friday morning for the murders of roommates Kaylee Goncalves, 21; Madison Mogen, 21, and Xana Kernodle, 20, as well as Kernodle's boyfriend, Ethan Chapin, 20.
Kohberger is a graduate student at Washington State University, located less than 10 miles away from the University of Idaho, Moscow Police Chief James Fry said at a Friday news conference.
The murder weapon has not been recovered, the chief said.
Jason LaBar, Kohberger's public defender in Pennsylvania, told ABC News on Monday that Bryan and his father Michael were pulled over twice in Indiana while driving from Pullman, Washington, to the Poconos, saying it was "approximately an hour apart, once for speeding, once for tailgating."
The pair were doing their preplanned, end-of-semester cross-country road trip, arriving at the family home on Dec. 13, 2022, exactly one month after the murders. They drove in the white Elantra, which is now being processed by authorities.
Washington State University identifies Kohberger as a Ph.D. student in its department of criminal justice and criminology. He completed his first semester in its criminal justice program earlier this month, the university said.
Within an hour of Kohberger being identified as the suspect, more than 400 calls came in to the Moscow Police Department's tip line, Fry said.
Kohberger is set to appear in Monroe County Court to face his charges, which include four counts of first-degree murder and burglary.
It is also the first step in his extradition to Idaho, where he will have another appearance.
Monroe County Chief Public Defender Jason LaBar, who is representing the suspect, previously said Kohberger "intends to waive his extradition hearing to expedite his transport to Idaho" and that he "is eager to be exonerated of these charges and looks forward to resolving these matters as promptly as possible."
Police have said they cannot reveal any information, including a motive or further details about how they tracked down Kohberger, until he is back in Idaho.
Many details of the case remain a mystery including a potential motive for the murders or how Kohberger knew the victims.
Authorities announced earlier this month that they were looking to speak with the driver of a white 2011-2013 Hyundai Elantra that was spotted near the victims' house around the time of the crime.
Asked at Friday's news conference if that car has now been found, the chief replied, "We have found an Elantra."
Fry later told ABC News Saturday that Kohberger is believed to be the only suspect in the high-profile case, authorities said.
"We believe we have our guy, the one that committed these murders," he said, adding that he does not anticipate any additional arrests.
Prior to attending Washington State University, Kohberger attended college at DeSales University, earning his bachelor's degree in 2020 and completing graduate studies in June 2022.
"As a Catholic, Salesian community, we are devastated by this senseless tragedy. Our thoughts and prayers are with the victims' families during this difficult time," the university said in a statement following his arrest.
ABC News' Kayna Whitworth and Timmy Truong contributed to this report.