Police in Moscow, Idaho, investigating the fatal stabbings of four University of Idaho students said Friday that they don't believe the two surviving roommates are involved in the crime.
The victims, who were killed in a house near campus early Sunday morning and found hours later, were identified as Ethan Chapin, 20, of Conway, Washington; Madison Mogen, 21, of Coeur d'Alene, Idaho; Xana Kernodle, 20, of Avondale, Arizona; and Kaylee Goncalves, 21, of Rathdrum, Idaho.
No suspects are in custody.
The victims were likely asleep at the time of the attack and each was stabbed multiple times, police said Friday, citing the coroner. Some had defensive wounds, police said. There is no indication of any sexual assault, the coroner said.
Two female surviving roommates were at the house at the time and were not hurt, according to Moscow Police Chief James Fry.
The Moscow Police Department also learned that Goncalves and Mogen used a private party for a ride home from Grub Truck at approximately 1:40 a.m. Police had previously said they used Uber, but later revised their statement.
It's believed the four students were killed between 3 a.m. and 4 a.m. Sunday, Moscow Mayor Art Bettge told ABC News.
The surviving roommates were home when police responded to a call for an unconscious individual at the home at about noon, Fry said. The roommates were not the 911 callers, according to Idaho State Police spokesman Aaron Snell. The 911 caller's identity hasn't been released.
Police on Friday also released a map and timeline of the whereabouts of the victims in the hours before the killings.
Goncalves and Mogen -- lifelong best friends -- were in downtown Moscow Saturday night while Chapin and Kernodle -- who were dating -- were at the Sigma Chi house, police said.
At about 1:40 a.m., Goncalves and Mogen were seen on video at the Grub Truck food vendor, and then they took a private vehicle home, arriving at 1:45 a.m., police said. Authorities said Friday that the man seen in the Grub Truck surveillance video with the victims is not believed to be involved in the crime.
Chapin and Kernodle also got home around 1:45 a.m., police said. Chapin didn't live in the house where they were killed, but was sleeping over with his girlfriend, according to his mother, Stacy Chapin.
Police are searching for leads and urge anyone who saw "suspicious behavior, has video surveillance, or can provide relevant information" to call the tip line at 208-883-7180 or email tipline@ci.moscow.id.us.
Fry said they were killed in "an isolated, targeted attack".
Latah County prosecuting attorney Bill Thompson told ABC News that authorities have "more information on the nature and location of the wounds" than they are releasing publicly.
He said police are not releasing certain details of the crime because there's some information that only the suspect would know.
MORE: 4 Idaho college students killed in 'targeted attack,' no suspects in custodyThe murder weapon has not been found, officials said.
Snell did not reveal what type of knife was used in the killings but said authorities are going to local businesses to see if anyone recently bought a fixed-blade knife.
Snell described it as "a very complex and in-depth investigation."
As for having no suspects nearly a week later, Snell said, "It's very frustrating ... we would have loved to have solved this [immediately]."
Police said Friday that they've received nearly 500 tips and have conducted 38 interviews. Police also said they've collected contents from three dumpsters to look for evidence.
Thompson said it's unusual to not have a suspect or motive at this point, and noted that this case has brought in more resources and manpower to Moscow than he's ever seen in his 30 years as prosecutor.
"I wish we had the answers," he said.
Goncalves and Mogen had been best friends since childhood and "did everything together," Goncalves' sister, Alivia Goncalves, told ABC News. She said she finds some solace that the friends were together in their final moments.
Although Fry described the attack as "targeted," he said Wednesday, "We cannot say there is no threat to the community."
ABC News' Kayna Whitworth, Nick Cirone and Timmy Truong contributed to this report.