Police were called to a house in Idaho last weekend to find the bodies of four university students.
It's still unclear what exactly happened to University of Idaho students Ethan Chapin, 20, Madison Mogen, 21, Xana Kernodle, 20, and Kaylee Goncalves, 21, after they returned home from a night of partying in the early hours of Sunday morning (13 November).
In what has been described by police as the most 'gruesome' and 'harrowing' crime scene they've ever seen, investigators understand that the four students were brutally killed between the hours of 3am and 4am using an 'edged weapon'.
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Local and State police have been working on the case with the FBI this week but, as of yet, no suspects have been arrested.
While authorities are keeping tight-lipped on the finer details of the investigation, police did confirm some facts about the fatal night.
Moscow Police Chief James Fry said in a press conference that all four victims had been out on Saturday night - Chapin and Kernodle at a party on campus and Mogen and Goncalves at a bar downtown - and all returned home after 1.45am.
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Although all four were killed in the early hours of the morning, there was no 911 call made until noon on Sunday.
It's not yet clear who made the 911 call, though Chief Fry did reveal that two other roommates were home at the time of the deaths, though neither were injured.
Officials also confirmed that there was no evidence of forced entry or a hostage situation, but the two surviving roommates have been fully cooperative with authorities, as per CNN.
The police chief noted that investigators aren't just looking at the two roommates right now, but 'focusing on everybody that may be coming and going from that residence'.
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Speaking to The Daily Mail about the quadruple homicide, a source close to the investigation described the crime scene as one of the worst they had ever seen.
Classes were cancelled at the University of Idaho on Monday, but the university's president Scott Green has confirmed that they have since resumed.
In a statement issued on Wednesday, Mr Green said that the university has 'continually pushed for as much information as possible' on the incident, but are wary of interfering with the investigation.
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While investigations continue, Chief Fry admitted that police could not definitively say that there was no further threat to the community, urging other students and campus residents to 'stay vigilant, report any suspicious activity and be aware of your surroundings at all times.'