DAVIS, Calif. — A 21-year-old man, who was a University of California, Davis, student until last week, has been arrested in connection with a harrowing series of three stabbings in the college town, the police announced on Thursday.

The man, Carlos Dominguez of Davis, was detained and booked on suspicion of murder after residents called the police with more than a dozen reports that they had seen a slight, young man who fit witnesses’ description of the suspect wandering near the park where one of the attacks happened, the police said.

Mr. Dominguez was carrying “a large fixed blade knife” when he was apprehended, the police said, and was booked into the Yolo County Jail early Thursday on suspicion of a weapons violation. He was arrested about 12 hours later on two counts of murder and a third count of attempted murder.

The announcement, which occurred just hours after a memorial service for one of the stabbing victims, was met with relief in the city of about 70,000 people west of Sacramento. The three stabbings over five days had shocked the residents of Davis, where the last reported homicide occurred in 2019.

“A murderer is off the streets and our families will sleep easier tonight,” said Will Arnold, the mayor. “Now the work begins, in earnest, to heal as a community, to take back our shared spaces and to move forward as one.”

The first victim was David Henry Breaux, 50, a Stanford University graduate who slept outdoors and was known to locals for a yearslong project in which he gathered and curated definitions of compassion. He was found dead at about 11:20 a.m. on April 27 in a park just east of the U.C. Davis campus where he routinely talked to residents at the city’s farmers’ market. Colloquially known as “the Compassion Guy,” Mr. Breaux had been stabbed “many, many times,” Darren Pytel, the police chief, said in a City Council meeting this week.

Two days after that first attack, Karim Abou Najm, 20, a student majoring in computer science at U.C. Davis, was killed on a bike path after an altercation in a neighborhood park at 9:14 p.m. on Saturday. A witness who lives near the path told the police that he had overheard a disturbance and rushed to the scene to find the student bleeding from multiple stab wounds. He described seeing a young, curly-haired man scrambling to get away on the victim’s bike.

The next morning, police arrested a 30-year-old “person of interest” within five blocks of where Mr. Abou-Najm was attacked, holding the individual on suspicion of illegally carrying a concealed knife, and on an outstanding felony warrant from a nearby county for public intoxication and resisting arrest. But as authorities expedited DNA analysis of evidence found at the two crime scenes, a woman in a homeless encampment east of the city’s downtown reported a third attack late Monday, saying she had been stabbed repeatedly through the wall of her tent.

The woman, Kimberlee Guillory, survived, the police said, adding that she remained hospitalized and was alert and improving. The victim and nearby witnesses described the assailant as a curly-haired young man in dark clothing who had been lurking near the encampment.

Before the arrest, anxiety mounted in the leafy cul-de-sacs, Little League fields and residence halls of Davis, a city where locals normally feel safe enough each summer to keep their windows open to capture the “Delta breeze” that blows from San Francisco Bay. This week, local businesses closed early, university events were canceled, and evening classes shifted to remote instruction. The farmers’ market canceled its scheduled Wednesday event.

The small Davis police force set up a tip line, moved to extended shifts and enlisted the help of local, state and federal law enforcement agencies to help process hundreds of reports. Social service departments ramped up outreach to unhoused people throughout the city, moving some two dozen into emergency quarters. The City Council scrapped its normal agenda for its Tuesday meeting so that Chief Pytel could update residents.

Then on Wednesday afternoon, calls came in about another person of interest. Carter Carlson, 23, an employee at the elementary school abutting the park where Mr. Najm died, said he was placing flowers on a makeshift memorial along the bike path when he noticed a lone figure, with a disheveled appearance, on the nearby play area behaving strangely. He called the police.

“He was pacing back and forth on a child’s bridge between two playgrounds,” said Mr. Carlson, whose job at the school involves intervening with children who are having difficulties.

He added that when another man entered the park, talking on his cellphone, the young man noticed and began to meander away, walking toward a local strip mall. Mr. Carlson hopped into his Honda Civic, he said, and followed him until he lost sight of him.

Shortly after, he said, he saw several police cars and, eventually, at about 5 p.m., police officers leading the man away.

A native of Davis, Mr. Carlson credited not only the police, but the community itself for the news Thursday.

“Everyone has been very shaken, and everyone has taken this very hard,” he said, “but this community has really come together to support those who have been so unfortunately attacked.”