Monday marks one year since four University of Idaho students were stabbed to death in a gruesome home invasion that garnered intrigue from people across the nation.
In the early hours of Nov. 13, 2022, roommates Kaylee Goncalves, Madison Mogen and Xana Kernodle, and Kernodle's boyfriend Ethan Chapin, were killed inside the girls' off-campus house in Moscow, Idaho. Two other roommates survived.
MORE: Idaho college murders: The complete timeline of eventsAfter an intensive six-week search for a suspect, 28-year-old Bryan Kohberger, a criminology Ph.D. student at nearby Washington State University, was arrested on Dec. 30 at his family's Pennsylvania home.
Here's what you need to know as the case against Kohberger moves forward:
One of the surviving roommates said she woke up around 4 a.m. on Nov. 13, 2022, from what sounded like Goncalves playing with her dog in one of the third-floor bedrooms, according to court documents.
"A short time" after, the roommate said "she heard who she thought was Goncalves say something to the effect of 'there's someone here,'" the documents said. But that could have been Kernodle on her phone because records showed she was on TikTok at about 4:12 a.m., the affidavit said.
MORE: Lawyer for Idaho college killings suspect Bryan Kohberger says he was driving alone night of murdersThe roommate said "she looked out of her bedroom but did not see anything when she heard the comment about someone being in the house," the documents said. "She opened her door a second time when she heard what she thought was crying coming from Kernodle's room."
The roommate "then said she heard a male voice say something to the effect of 'it's ok, I'm going to help you,'" according to the documents.
The roommate said she opened her door again after she heard the crying -- and then saw a "figure clad in black clothing and a mask that covered the person's mouth and nose walking towards her," who she described as "5'10" or taller, male, not very muscular, but athletically built with bushy eyebrows," and who "walked past" her "towards the back sliding glass door" as the roommate stood in "frozen shock," according to a police affidavit.
Kaylee Goncalves, 21, and Madison Mogen, 21, were lifelong best friends and inseparable. Goncalves was set to graduate in December 2022 and move to Texas.
Goncalves' sister, Alivea Goncalves, considered Mogen a sister, too. She said she was comforted by the fact that the best friends were in the same bed together in their final moments.
"If I couldn't have been there to hold their hands and to take that pain from them, at least they had each other," she told ABC News.
The two other victims were 20-year-old Xana Kernodle, and her boyfriend, 20-year-old Ethan Chapin.
Chapin was a triplet. His brother and sister also attend the University of Idaho.
Chapin and Kernodle were the "perfect pair" who had an "unstoppable, loving relationship," a surviving roommate said in a statement in December.
"They both would look at each other with so much love," she said.
After the victims were discovered, authorities reviewed surveillance video from the area and saw the suspect's white Hyundai Elantra go by the victims' house three times, before entering the area for a fourth time at 4:04 a.m, according to the affidavit.
Police said they traced the car's travel that night back to nearby Pullman, Washington, where the suspect lived while attending Washington State.
Kohberger's phone was tracked heading to Moscow before the attack and as the driver of the white Elantra returned to Pullman. However, the phone was off from 2:47 a.m. to 4:48 a.m., which "is consistent with Kohberger attempting to conceal his location during the quadruple homicide," the document said.
MORE: Idaho authorities probe Amazon 'click activity' for knives possibly connected to college killingsHis phone was near the victims' house at least 12 times before the murders, at least as far back as August, the document said.
DNA from the suspect was also recovered on a knife sheath left on Mogen's bed, according to the documents.
Kohberger is charged with four counts of first-degree murder and one count of burglary. He could face the death penalty if convicted.
The former Ph.D. student declined to offer a plea at his arraignment in May, so the judge entered a not guilty plea on his behalf.
MORE: Trial for Idaho college killings suspect Bryan Kohberger delayed indefinitelyKohberger's lawyers have said their client wasn't in the home where the homicides occurred and was driving around alone that night.
In August, Kohberger waived his right to a speedy trial, indefinitely delaying what was supposed to be an Oct. 2 start date.
A new trial date has not been set.
The DNA discovered on the button snap of the knife sheath that was found near Mogen's body is a critical linchpin for the prosecution in what is a largely circumstantial case.
That DNA, authorities argued, undeniably links Kohberger to the crime scene, saying that DNA "showed a statistical match" with a cheek swab taken directly from Kohberger after his arrest.
Kohberger's attorneys have attempted to cast doubt on the strength of investigators' evidence and whether it pointed irrefutably to just their client, including the DNA. The defense has repeatedly asked for more information on the genealogical analyses used to zero in on Kohberger, and have pushed back on investigators' analysis that the DNA is a statistical match.
Kohberger's attorneys also highlight what they called a "total lack of DNA evidence" from the victims in Kohberger's home or car.
"There are so many layers that make this an extraordinary case -- and the defense is going to attack any aspect of it that they see as vulnerable," David Calviello, a former New Jersey prosecutor who is now a criminal defense attorney, told ABC News in August. "It makes sense for them to take shots at how certain evidence was presented to the grand jury -- whether there were missed steps, cut corners, chain of custody problems, contamination -- or not. "
The knife used in the murders has not been recovered.
A series of now-unsealed search warrant documents show investigators have sought records of Amazon purchases and click history data for an Amazon customer including "all detailed customer click activity pertaining to knives and accessories," as well as a long list of information that could flesh out the customer's full shopping movements and interests on the site, like items that were wish-listed or saved for later. If prosecutors can link Kohberger to the purchase of a knife that could have been used in the killings, experts say that could help bolster their case.
The University of Idaho announced in February that the house where the four students were killed would be torn down, with university President Scott Green calling it "a healing step."
In June, a university spokesperson said the school planned to demolish the house before students returned to campus in the fall.
In July, the university announced a sudden halt to the demolition plans as they removed asbestos and lead from the home -- and amid objections from some of the victims' families who expressed concern that demolishing the house before Kohberger's trial could cause unanticipated problems for prosecutors as they try to secure a guilty verdict.
About two weeks after Kohberger waived his speedy right to a trial in August, university officials decided they would hold off on tearing down the home until at least the end of the fall semester, which ends in mid-December.
With no new trial date set, prosecutors asked the University of Idaho for access to the house.
The university said FBI agents would be at the house on Oct. 31 and Nov. 1 "to get documentation to construct visual and audio exhibits and a physical model of the home."
"While the university still intends to demolish the home, it will not be done this semester," the university said on Oct. 31.
Ethan Chapin, who was a triplet, had been planning his 21st birthday with his siblings "forever," his parents said. Last month, his brother, Hunter, and sister, Maizie, turned 21 without him.
As the Chapins face one year without Ethan, they said they plan on acknowledging Nov. 13 with a private fundraiser for their foundation, Ethan's Smile Foundation, to help provide scholarships to post-high school students so that they can follow their dreams. The Chapins said they can't think of a better way to honor their son than to support education.
"Ethan stood for love, kindness, laughter and loyalty," his mother, Stacy Chapin, told ABC News. "He was the very best."
Kaylee Goncalves' dad, Steve Goncalves, said Kaylee's younger siblings are now grappling with their own birthdays. He said "they don't want to be older than their sister."
To Steve Goncalves, Nov. 13 is not an anniversary.
"This is more like a memorial -- some type of an event that you have to look at and think about, but it's not something that you ever look forward to," he told ABC News.
"My daughter has allowed me to meet people across the world through her life and memory and her beauty. And I'll thank her one day when I see her," Steve Goncalves said. "I'll tell her how much she impacted the world and how proud of her I am."
FOLLOW THE PODCAST: "The King Road Killings: An Idaho Murder Mystery" from ABC News, available on Apple Podcasts, Spotify, Amazon Music, or your preferred podcast player.
ABC News' Kayna Whitworth, Nick Cirone and Timmy Truong contributed to this report.