The prosecutor said investigators believe Bryan Kohberger broke into the students' home "with the intent to commit murder."
CHESTNUTHILL TWP., Pa. (WPVI) -- A 28-year-old man was arrested Friday in Pennsylvania's Pocono Mountains region on first-degree murder charges in the killings of four University of Idaho students last month.
Bryan Christopher Kohberger appeared before a judge earlier Friday. Court documents show the judge ordered Kohberger's extradition to Idaho where he will face criminal charges.
Sources say that authorities knew who they were looking for and had tracked Kohberger to his parent's home on the 100 block of Lamsden Drive in Chestnuthill Township, Monroe County.
Law enforcement sources told ABC News police in Idaho identified Kohberger as a suspect, at least in part, by using DNA technology. They tracked him to Pennsylvania through his vehicle.
The FBI had been watching the house for several days before a specialized team of state troopers and federal agents moved in and took him into custody around 2 a.m., sources say.
Authorities are still working to investigate how Kohberger was connected to the victims.
Moscow (Idaho) Police Chief James Fry said they're still "putting all the pieces together" to determine a motive.
The affidavit for four charges of first-degree murder in Idaho will remain sealed until he is returned. He is also charged with felony burglary in Idaho, Latah County Prosecutor Bill Thompson said. An extradition hearing is scheduled for Tuesday.
Idaho authorities have been looking for a white Hyundai Elantra in connection with the murders.
WATCH | Idaho authorities update public after college murder suspect's arrest
A neighbor, who did not want to be identified, tells Action News that one was towed from the Kohberger home on Friday morning.
"The tow truck came, they towed the car. We were surprised because we didn't know what was going on," she said.
When shown a picture of an Elantra, she said, "Yes, that's the car."
"We've seen the owner drive that car so many times," she said.
The neighbor said she didn't know Kohberger but she had seen him in and out of the house in recent weeks. She said his parents are a "very sweet couple."
Fry confirmed Friday that an Elantra had been found. However, investigators are still looking for the murder weapon.
Thompson said investigators believe Kohberger broke into the students' home "with the intent to commit murder."
The stabbing deaths shook the small town of Moscow, Idaho, a farming community of about 25,000 people - including roughly 11,000 students - tucked in the rolling hills of northern Idaho's Palouse region.
The victims, Kaylee Goncalves, 21; Madison Mogen, 21; Xana Kernodle, 20; and Kernodle's boyfriend, Ethan Chapin, 20; were likely asleep when they were each stabbed multiple times in the early hours of November 13, authorities have said.
Some of the victims had defensive wounds, a coroner has said. There was no sign of sexual assault, police said
The killings happened in the girls' off-campus house.
Two other roommates -- who police said are not suspects -- survived and likely slept through the murders, according to officials. The survivors were on the ground floor while the four victims were on the second and third floors.
Goncalves' family told ABC News on Friday that they don't know Kohberger but are seeing connections between two that they aren't ready to discuss yet. The family said they are "happy, relieved and thankful" that there's been an arrest.
Kohberger is a Ph.D. student at Washington State University, which is a short drive across the state line from the University of Idaho.
He graduated from Northampton Community College in Pennsylvania with an associate of arts degree in psychology in 2018, said college spokesperson Mia Rossi-Marino.
Kohberger received his bachelor's degree in 2020 from DeSales University near Allentown, Pennsylvania, and completed his graduate studies in June 2022. The university is located about 40 miles south of where he was arrested.
"As a Catholic, Salesian community, we are devastated by this senseless tragedy," the university said in a statement. "Our thoughts and prayers are with the victims' families during this difficult time."
According to ABC News, a user on Reddit identifying themselves as Bryan Kohberger and a criminology student at DeSales University posted multiple times several months ago recruiting "research participants" for a university study.
In the posts, which were made starting in May 2022, the user asked for information to help a "research project that seeks to understand how emotions and psychological traits influence decision-making when committing a crime." The posts linked to a survey that asked detailed questions about committing crimes.
A source tells ABC News that law enforcement is aware of the Reddit posts.
Police said they have received about 20,000 tips through more than 9,025 emails, 4,575 phone calls, and 6,050 digital media submissions, while having conducted over 300 interviews in the case of the four students slain in an off-campus home.
Fears of a repeat attack prompted nearly half of the University of Idaho students to switch to online classes for the remainder of the semester, abandoning dorms and apartments in the normally bucolic town for the perceived safety of their hometowns.
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.
All four were friends and members of the university's Greek system. Xana Kernodle, 20, was a junior studying marketing. She was from Post Falls, Idaho, and joined the Pi Beta Phi sorority on campus. She lived at the rental home with the other two women who were stabbed, and she was dating Ethan Chapin, who was visiting the night of the killings.
Chapin, also 20, was from Conway, Washington, and was a triplet. His brother and sister also attend UI, and both Chapin and his brother were members of the Sigma Chi fraternity.
Kaylee Goncalves and Madison Mogen were both 21 and friends who grew up together in northern Idaho. Mogen worked with Kernodle at a Greek restaurant in Moscow. She was also a member of Pi Beta Phi.
Goncalves was a senior majoring in general studies, a member of the Alpha Phi sorority and was planning a trip to Europe next year.
Goncalves and Mogen went to a bar, stopped at a food truck and then caught a ride home around 2 a.m. on Nov. 13, according to a police timeline of the evening.
Chapin and Kernodle were at the Sigma Chi house just a short walk away and returned to Kernodle's house around 1:45 a.m., police said.
Two other roommates who live in the home were also out that evening, but returned home by 1 a.m., police said. They didn't wake up until later that morning.
After they woke up, they called friends to come to the house because they believed one of the victims found on the second floor had passed out and wasn't waking up. At 11:58 a.m., someone inside the home called 911, using a roommate's cell phone. Multiple people talked with the dispatcher before police arrived.
Police found two of the victims on the second floor of the three-story home, and two on the third floor. A dog was also at the home, unharmed.
Autopsies showed the four were all 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.
ABC News, the Associated Press and the CNN Wire contributed to this report