(CNN) It's been more than two weeks since the stabbing deaths of four students at an off-campus home, and with no suspect or arrest, "people are kind of sketched out" as they return to campus from Thanksgiving break, one student said Monday.
"It definitely feels a little bit different," said student Hayden Rich. "It's kind of a different vibe. It seems kind of a sad setting. It is kind of quiet."
With a killer on the loose, it's unclear how many students will actually come back to Moscow, Idaho, for the last two weeks of classes before winter break.
Student Ava Forsyth said her roommate is staying home because she does not feel safe. Forsyth said she feels "moderately" safe, but "not so much" at night, when she takes advantage of a free campus walking security service.
University of Idaho President Scott Green acknowledged last week that some students did not want to return until a suspect is in custody.
"As such, faculty have been asked to prepare in-person teaching and remote learning options so that each student can choose their method of engagement for the final two weeks of the semester," he wrote in a statement.
Rich said he decided to come back for the many tests he has this week. Student Lexi Way told CNN that she feels safe with upped campus security, and "tends to learn better in class."
The university has scheduled a vigil for Wednesday to commemorate the victims.
Dozens of local, state and federal investigators are still working to determine who carried out the brutal attack. Investigators have yet to identify a suspect or find a weapon -- believed to be a fixed-blade knife -- and have sifted through more than 1,000 tips and conducted at least 150 interviews.
The four students -- Ethan Chapin, 20; Kaylee Goncalves, 21; Xana Kernodle, 20; and Madison Mogen, 21 -- were found stabbed to death on November 13 in an off-campus home in Moscow. The killings have unsettled the campus community and the town of about 25,000, which had not seen a murder since 2015.
Police said they believe the killings were "targeted" and "isolated" but have not released evidence to back up that analysis. They also initially said there was no threat to the public -- but later backtracked on that assurance.
"We cannot say there's no threat to the community," Police Chief James Fry said days after the killings.
Authorities said they have not ruled out the possibility that more than one person may be involved in the stabbings.
In the meantime, a former student told CNN's Paula Reid on Sunday that she's raised more than $19,000 to buy and distribute personal alarms to students as a way to increase safety on campus.
"It's been completely overwhelming in the best possible way," said the former student, Kerry Uhlorn. "Something that started so very, very small, has just exploded and it's amazing to see the community come together like this."
So far, using the evidence collected at the scene and the trove of tips and interviews, investigators have been able to piece together a rough timeline and a map of the group's final hours.
On the night of the killings, Goncalves and Mogen were at a sports bar, and Chapin and Kernodle were seen at a fraternity party.
Investigators believe all four victims had returned to the home by 2 a.m. the night of the stabbings. Two surviving roommates had also gone out in Moscow that night, police said, and returned to the house by 1 a.m.
Police earlier said Goncalves and Mogen returned to the home by 1:45 a.m., but they updated the timeline Friday, saying digital evidence showed the pair returned at 1:56 a.m. after visiting a food truck and being driven home by a "private party."
The next morning, two surviving roommates "summoned friends to the residence because they believed one of the second-floor victims had passed out and was not waking up," police said in a release. Somebody called 911 from the house at 11:58 a.m. using one of the surviving roommates' phones.
"The call reported an unconscious person," Moscow Police Capt. Roger Lanier said Wednesday. "During that call, the dispatcher spoke to multiple people who were on scene."
When police arrived, they found two victims on the second floor and two victims on the third floor. There was no sign of forced entry or damage, police said.
Investigators do not believe the two surviving roommates were involved in the deaths.
A coroner determined the four victims were each stabbed multiple times and were likely asleep when the attacks began. Some of the students had defensive wounds, according to the Latah County coroner.
At least 113 pieces of physical evidence have been collected, about 4,000 crime scene photographs were taken and several 3-D scans of the house were made, according to police. Detectives also collected the contents of three dumpsters on the street in case they held any evidence.
In an effort to locate the weapon, investigators contacted local businesses to determine if a fixed-blade knife had been purchased.
More than 260 digital submissions, which could include photos and videos, have been submitted by the public to an FBI tip form, the Moscow Police Department said in a release Friday. The department is asking for any tips or video footage of the places the victims went that night, even if there is no discernible movement or content in them.
"Detectives are also seeking additional tips and surveillance video of any unusual behavior on the night of November 12th into the early hours of November 13th while Kaylee and Madison were in downtown Moscow and while Ethan and Xana were at the Sigma Chi house," the release said.
In addition, Idaho Gov. Brad Little has committed up to $1 million of state emergency funds to assist the ongoing investigation, state police said.
As the weeks stretch on without a named suspect or significant advances in the case, a flurry of rumors has arisen about the killings. Moscow police addressed the issue in a news release Friday and attempted to quash some of the hearsay.
"There is speculation, without factual backing, stoking community fears and spreading false facts. We encourage referencing official releases for accurate information and updated progress," the release said.
Several people have been ruled out as suspects for the time being, the police department said, including:
The police also said reports that the victims were tied or gagged are inaccurate and stressed that the identity of the 911 caller has not been released.
Correction: An earlier version of this story misspelled the name of Kerry Uhlorn.