The small college town of Moscow is reeling after four University of Idaho students were savagely murdered more than one week ago – and a series of puzzling questions remain unanswered.

Ethan Chapin, 20, Xana Kernodle, 20, Madison Mogen, 21, and Kaylee Goncalves, 21, were stabbed to death Nov. 13 between 3 and 4 a.m. on the second and third floor of a rented house near campus and fraternity row.

Investigators, amateur online sleuths and the victims' families are desperately searching for clues – alongside the Moscow Police Department, Idaho State Police and the FBI.

Latah County Coroner Cathy Mabbutt said the victims were likely ambushed in their sleep with a large knife – and some of the slain students had defensive wounds, suggesting a violent struggle. 

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 Yet two other roommates, who were home at the time, didn't appear notice any commotion and police weren't called more than eight hours.

"How do you take four lives and no one hears?" Joseph Morgan, distinguished scholar of applied forensics at Jacksonville State University, told Fox News Digital. "This sent shivers up my spine." 

Officials have not identified any suspects or persons of interests in the killings or determined whether the attack was perpetrated by more than one assailant.

The coroner previously said the killer(s) likely used a large knife to stab each of the victims multiple times in the chest – but police have not recovered a murder weapon.

Retired NYPD Sgt. Joseph Giacalone said that the investigation is complicated by the most of the students leaving town for the holidays. 

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"If the killer is a fellow student, he's long gone," he said.

Officials told Fox News Digital that they hadn't zeroed in any potential motives and that all options remained on the table – including a crime of passion and a robbery gone awry.

Mabbutt said there was no sign any of the victims had been sexually assaulted. But the nature of the crime suggested it was personal, said Morgan. 

"This is passionate crime," he said. "You have an individual who was willing to get so close that he could feel the breath of his victim when he drove the knife into their chests."

He added that a crime can still be sexually motivated in the absence of a sexual assault.

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Gascolane agreed that the nature of the crime suggested the assailant(s) knew his victims. "Strangers can't get you that mad," he noted.

The surviving roommates summoned friends to the King Road home because they believed one of the victims on the second floor had passed out, police revealed Sunday at a press conference.

At 11:58 a.m. a 911 call made from one of the surviving roommates' cell phones requested aid for an unconscious person. Multiple people spoke to the dispatcher before police arrived.

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Police have not disclosed who made the initial call – but have cleared the surviving victims and the friends as suspects.

The property manager, Merida McClanahan, told Fox News Digital that the single-family home has two bedrooms on each floor with bathrooms and hallways in between them. 

On the second floor, the rooms are separated by a living room and kitchen area.

The victims were found on the second and third floors. Police did not say which floor was occupied by the two surviving roommates. 

"This a college town. It's not unusual for students living together to disregard loud music, laughing and screaming," retired NYPD Det. Herman Weisberg told Fox News Digital. "It's likely noises that would disrupt a normal household would go unnoticed in this environment."

Fox News' Audrey Conklin contributed to this report.