(CNN) The four University of Idaho students who were found stabbed multiple times in their off-campus home were "likely asleep," before they were attacked, Moscow, Idaho, police said in a Friday evening update.
In the update, posted on Facebook, authorities released several new details about the gruesome killings that left the university's community in shock and grief.
Detectives have conducted 38 interviews with people "who may have information" about the killings, the update said, and took the contents of three dumpsters on the road the house was located on in case there was evidence. Investigators also asked local businesses if there had been any recent purchases of a "fixed-blade knife," the update said.
There are no suspects in custody and the weapon has not been found, police said.
The four college students -- Ethan Chapin, 20; Kaylee Goncalves, 21; Xana Kernodle, 20; and Madison Mogen, 21 -- were found stabbed to death Sunday in their shared off-campus home near the university.
The victims were found on the second and third floors of the home, Idaho State Police Communications Director Aaron Snell told CNN earlier on Friday.
Latah County Coroner Cathy Mabbutt told CNN she saw "lots of blood on the wall" when she arrived at the scene. She confirmed there were multiple stab wounds on each body -- likely from the same weapon -- but would not disclose how many wounds nor where most were located.
Stab wounds on the hands of at least one victim appear to be defensive wounds, according to Mabbutt. She said there was no sign of sexual assault on the bodies during the autopsies.
In their Friday evening update, police said "some" of the victims had defensive wounds.
The university announced Friday a candlelight vigil in memory of the four students will take place on campus November 30.
"Please join us from where you are, individually or as a group, to help us light up Idaho," the university's website said. "Light a candle, turn on stadium lights, or hold a moment of silence with us as we unite on campus."
Hoping for tips from the community, investigators on Friday released a map and timeline of the victims' movements last weekend. The map shows the four students spent most of the night separated in pairs.
Chapin and Kernodle attended a party at the Sigma Chi fraternity house from 8 p.m. to 9 p.m. local time Saturday.
Goncalves and Mogen were at the Corner Club sports bar between 10 p.m. and 1:30 a.m. They picked up food at a food truck at 1:40 a.m. before heading home.
The four victims were back at the house by 1:45 a.m. Sunday.
Two other roommates were home at the time of the attack and were found uninjured, Moscow Police Department Chief James Fry said earlier this week.
Investigators are speaking with the two surviving roommates, Snell told ABC.
"Potentially they are witnesses, potentially they are victims," Snell said in an interview with ABC's Kayna Whitworth. "Potentially they're the key to this whole thing."
Police have said they don't have a suspect. Snell said no one has been "included or excluded as a person of interest and/or a suspect."
In their Friday evening update, police said they "do not believe" the two surviving roommates or a male seen in the food truck surveillance video were involved in the crime.
Autopsies were conducted on November 17, police said late Friday. The Latah County Coroner confirmed the cause and manner of death of the students was homicide by stabbing, police said.
The killings, which happened little more than a week before Thanksgiving break, have instilled harrowing sentiments among students as authorities investigate leads to identify a suspect or locate a murder weapon.
The university's often-packed parking lots had many empty spots Thursday after scores of students decided to return home or leave the area.
"Everybody kind of just went back home because they're scared. ... It's definitely uneasy on campus right now," student Nathan Tinno told CNN.
Tinno, who said the community is trying to approach the tragedy with sympathy, added the fact that no perpetrator has been caught in the case has elevated the sense of fear on campus.
"It's so dark. It's just like a dark cloud over everything," Ava Driftmeyer said. "We're leaving as fast as we can."
Driftmeyer, who said she lives near where the four students were killed, described how it has been a difficult situation to process, both mentally and emotionally.
"I just don't even think it's like set in yet. ... You know how insane this is? And the fact that there's no answers is like the worst feeling ever," she said.
Police said Wednesday they could not definitively determine the public was not a risk, backtracking an earlier statement that the attacks were targeted.
"We cannot say there's no threat to the community," Fry said Wednesday during a news conference. "And as we have stated, please stay vigilant, report any suspicious activity and be aware of your surroundings at all times."
The university also reminded students mental health support is available for them.
"We are all still working though our grief and a range of emotions. Compounding this is the frustration and concern that no one has been arrested for these crimes," university president Scott Green said in a statement.
"Students, you are encouraged to do what is right for you. Whether this is going home early or staying in class, you have our support," Green added.
As many details remain unclear, one of the victim's parents revealed his child's struggle with the attacker.
The father of Xana Kernodle said he spoke with his daughter at midnight Sunday, just hours before she was attacked and killed. Citing an autopsy, he said she fought off her attacker through the end.
"Bruises, torn by the knife. She's a tough kid," Jeffrey Kernodle told CNN affiliate KPHO/KTVK in Avondale, Arizona.
Kernodle said Xana stayed in regular communication with her family. "I think midnight was the last time we heard from her, and she was fine," he told the station, adding he doesn't understand why his daughter and her roommates were killed in their own home.
"They were just hanging out at home. Xana was just hanging out at home with her boyfriend," he said.
Kernodle said the door of the home opened with a number code.
"So, they either knew that or they just kind of went around and found the slider [sliding door] open," he told KPHO/KTVK.
Goncalves' sister, Alivea Goncalves told ABC World News Tonight there was a keypad door lock on the door and "my sister was always a door locker."
But, the sister added, "This was the party house, and it's been generations, so I won't say they were very private with that code."
Just hours before the four students were killed, Goncalves had posted a photo of the group with the caption, "one lucky girl to be surrounded by these ppl everyday," adding a heart emoji.
A TikTok video from Goncalves' account posted October 27 shows Goncalves and the two other female victims, Kernodle and Mogen. The video shows the women pretending to be each other in a humorous context, offering a glimpse into their lives.
"All of this is so confusing to us because Kaylee's not stupid," Alivea Goncalves told Inside Edition. "She's a smart girl. She's a strong girl. She's a mean girl. She's a fighter."
The scant information available regarding the case has been frustrating those closest to the victims as well as the campus community. Yet a video showing two of the victims has helped police get a clearer idea of the hours leading up to the homicides.
In a live Twitch stream from a food truck called Grub Truckers, Mogen and Goncalves were last seen alive while ordering $10 worth of carbonara around 1:40 a.m. local time Sunday in Moscow. As they waited for about 10 minutes for their food, they chatted with each other as well as other people standing by the truck.
Joseph Woodall, who manages the food truck, told CNN the two students did not seem to be in distress or in danger in any way.
Chapin and Kernodle were at a party on campus Saturday night, Fry said. All four students returned home early Sunday sometime after 1:45 a.m., Fry added.
Later Sunday morning, the four were killed inside their home, authorities said. Police responded to the residence after receiving a 911 call around noon reporting someone was unconscious.
Authorities have not released the identity of the 911 caller.
When police arrived at the home, they walked into a grisly, bloody crime scene.
"It was a pretty traumatic scene to find four dead college students in a residence," coroner Mabbutt told CNN affiliate KXLY earlier this week.
All four were pronounced dead at noon, and police have not revealed who made the 911 call.
"They were smart, they were vigilant, they were careful and this all still happened," Goncalves' older sister, Alivea, said in a statement on behalf of the family to the Idaho Statesman.
"No one is in custody and that means no one is safe. Yes, we are all heartbroken. Yes, we are all grasping. But more strong than any of these feelings is anger. We are angry. You should be angry."
Correction: A previous version of this story incorrectly attributed information from authorities to university president Scott Green.