The man was taken into custody Friday in Monroe County in northeastern Pennsylvania.
Arrest paperwork obtained by The Associated Press said 28-year-old Bryan Christopher Kohberger was being held for extradition to Idaho on a preliminary charge of first-degree murder.
A student with the same name is enrolled at Washington State University in Pullman, Washington, just across the Idaho state line from Moscow, and is pursuing a doctorate related to criminal justice and criminology.
Police in Moscow, Idaho, have scheduled a press conference for 1 p.m. PST Friday, likely to share more information about the arrest.
Law enforcement officials told NBC New York a white Hyundai Elantra was found outside the man’s home. Moscow police had previously asked for help finding a similar vehicle that was seen in the area at the time of the slayings.
Kaylee Goncalves, 21; Xana Kernodle, 20; and Madison Mogen, 21, lived at the house where the bodies were discovered. A visitor, Ethan Chapin, 20, who was dating Kernodle, also was slain.
Police initially described the killings, which left the small college town on edge, as an isolated and “targeted” incident with no broader threat to the general public.
The department later clarified that it was unsure if the occupants of the house were specifically targeted or if the target was the residence itself.