(CNN) — Officials in Davis, California, have lifted an overnight shelter-in-place order after they were unable to find a suspect in a knife attack late Monday — the third such incident following two fatal stabbings in less than a week near the campus of the University of California, Davis.

The startling order not to venture out followed Monday’s stabbing, which left a woman in critical condition. That attack was preceded by the killings Saturday evening of UC Davis senior Karim Abou Najm and Thursday of 50-year-old David Breaux at different parks near campus.

Authorities are combing through hundreds of tips, but they have not positively linked the three attacks, which Davis Police Chief Darren Pytel said in a news conference Tuesday were “particularly violent and brazen.”

Pytel highlighted the similarities between them: The two “particularly brutal” homicides occurred in city parks, he said, while the suspect or suspects in the second homicide and Monday night’s attack both interacted with witnesses. That suggests bold behavior that causes police “significant concern,” Pytel said.

Police received a call about the third stabbing at 11:46 p.m. Monday, according to a news release from the city, which said the attack “occurred in a known transient camp” around 2nd and L streets.

Police first received a 911 call about a disturbance at a tent there, Pytel said, which was soon followed by a 911 call from the female victim, who reported being stabbed. She was taken to UC Davis Medical Center, where she is in the ICU in critical but stable condition.

Officers from the Davis Police Department did not locate the suspect after a “detailed search” overnight of downtown, the department said in a statement. The shelter-in-place order was being lifted, but residents were urged to “continue to be aware of your surroundings.”

City officials described the suspect as a man with curly hair, a thin build and a light complexion between 5-foot-6 and -9 inches tall. He was wearing a black or blue sweatshirt, black pants with white stripes and was carrying a brown backpack.

The descriptions of the suspects in Saturday’s killing and Monday’s attack are “substantially similar,” Pytel said.

The suspect in Saturday’s deadly knife attack is believed to be a “light-skinned male, possibly Hispanic,” between 19 and 23 years old and between 5 feet, 7 inches and 5 feet, 8 inches tall” with long curly hair, city police in Davis, California, said Sunday in a news release.

The FBI has joined state and local law enforcement in a manhunt for the suspect, which Henry said involves every agency within the county with help from neighboring jurisdictions. Investigators are focused on analyzing the physical evidence while combing through tips, which quickly rose after police provided a description of the attacker Saturday, Pytel said.

“We are looking for DNA that will help us find the offender,” Pytel said at Tuesday’s news conference, adding physical evidence has been submitted to crime labs in hopes of finding a common thread.

Pytel also noted there is no city surveillance and no video showing any of the attacks.

“We are bringing in every resource and working around the clock to be able to solve these horrific crimes,” Deputy Chief Todd Henry told CNN Tuesday, adding the public should remain vigilant. “Look out for each other, stay aware of your surroundings.”

‘Everyone’s really scared,’ student says

Police were alerted to Breaux’s killing last Thursday morning, when officers responded to a welfare check at Central Park and found the 50-year-old slouched over on a park bench where he often sat or slept, Pytel said Tuesday. The preliminary investigation revealed Breaux had suffered multiple stab wounds.

On Saturday night, a resident reported hearing a disturbance near his home in nearby Sycamore Park. When the resident went outside to investigate, he found a man — later identified as Abou Najm — with multiple stab wounds, Pytel said. He also had a brief interaction with the suspect, who then fled.

About 40,000 students are enrolled at the public university in Davis, a city of some 68,000 people about a 20-minute drive west of the state capital, Sacramento.

Extra officers were being deployed to patrol around schools and parks, the Davis Police Department said Sunday, adding it “understands the uncertainty, fear and panic that is arising in the community.”

“At this time, it is strongly recommended that the community remain vigilant, be aware of your surroundings, and call the Davis Police Department if anyone acting violent, suspicious or matching the description provided is seen,” police said.

While Davis is not implementing a curfew, Pytel said Tuesday, it is “stepping up patrols all over town.”

“Our intent is to have a very visible presence,” he added.

UC Davis student Brayden Chipman, a classmate of the victim in Saturday’s killing, told CNN affiliate KCRA prior to the third stabbing that the rash of attacks was worrying.

“Definitely a bit concerning, because you never hear of this stuff happening here. It’s seen as like a safe community,” Chipman said. “It’s just really sad that a lot of students are just now fearing for their lives.”

Kristin Mifsud, another student, echoed that, telling CNN affiliate KOVR, “Murders don’t really happen here.”

“Everyone’s really scared,” Mifsud said. “I have seen a lot on social media that no one even wants to go to school.”

Extra patrols also were being added on campus and the UC Davis Police Safe Rides Program, which offers free rides and walking escorts to students on campus after dark, would expand, UC Davis Chancellor Gary May announced Sunday, calling the student’s death “deeply unsettling.”

UC Davis Police announced Monday evening the school had enlisted additional personnel through a private Sacramento-based security firm.

A community mourns

Abou Najm’s family told KCRA the 20-year-old was coming home from an undergraduate award ceremony when he was killed.

“I want this to be his memory: a bundle of energy, a bundle of positivity,” Majdi Abou Najm said of his son. “Someone who was full of ambition, proud of his roots, who just wanted to make this world a better place.”

The computer science major had a bright future ahead of him, according to Chipman, one of his classmates, who said Abou Najm “had a lot of opportunities, research, internships.”

“Someone got robbed of their future,” Chipman told the affiliate. “It’s just heartless, people doing things like that. Seeing someone that I know, it’s just felt a little deeply. It’s really sad.”

Breaux, the first attack victim, was a fixture in the community known as “Compassion Guy,” according to a statement from the mayor and City Council that said he regularly asked passersby about their views on compassion.

“The death of David Breaux is utterly and completely devastating,” Davis Mayor Will Arnold said. “Many of us knew David. We talked with him. We shared in his vision for a kinder world. We connected on what it means to be human and humane.”

3rd stabbing in a week near UC Davis leaves campus on edge as officials lift overnight shelter-in-place order