A first-year student in the University of New England’s College of Osteopathic Medicine was stabbed to death Saturday morning inside a public library in Massachusetts.

The victim was identified Sunday as Deane “Kenny” Stryker, 22, who had been a medical student at the university’s Biddeford campus since August.

Stryker was seated in the reading room of the Winchester Public Library and studying or reading when Jeffrey Yao, 23, approached her from behind and stabbed her in the head and upper torso with a 10-inch-long hunting knife, Middlesex County District Attorney Marian Ryan told reporters during a news conference.

Ryan said Stryker, who was from Winchester, staggered toward the door where several people tried to help her, including a 77-year-old man who was stabbed in the arm by Yao. Authorities said the man will survive his wound. Winchester Police Chief Peter MacDonnell credited library patrons with restraining Yao until police arrived.

Yao is scheduled to be arraigned Monday morning in Woburn District Court on charges of murder and armed assault with intent to murder. The motive for the stabbing remains under investigation, though he is known to police, Ryan said. When asked if Yao had mental health or drug addiction issues, Ryan said those factors are being looked at as part of the ongoing investigation.

The news of Stryker’s slaying stunned the UNE community.

“I was shocked and saddened to learn of the death of one of our students,” UNE President James Herbert said in a statement posted Sunday evening on the university’s Facebook page. “We send our deepest condolences to Deane’s family and friends, who are facing an unthinkable tragedy.”

“Deane was just beginning her journey toward becoming a physician and showed great promise as a student doctor who was passionate about medicine and helping others,” Herbert said. “She was an advocate for domestic violence and mental health awareness, and an active member of her college community.”

Herbert said Stryker served as an orientation leader and was part of a student organization that provides confidential peer support to other UNE students who need someone to turn to when they are struggling.

Dora Anne Mills, UNE’s vice president for clinical affairs, said Sunday night that she met Stryker in October at a daylong university-sponsored conference on opioid addiction and treatment.

Though she did not know Stryker on a personal basis, Mills said she was impressed with Stryker and her fellow medical students – about 100 attended – because it was a beautiful October day and the conference was elective.

UNE’s College of Osteopathic Medicine is a highly competitive four-year program, with the majority of the graduates moving on to become primary care physicians. Most of the first- and second-year students rent homes in the Biddeford area.

Since UNE is not on school break, Stryker likely would have had classes Monday, Mills said.

“It’s a very tight-knit group. The first-year students spend a lot of time together in study groups with six to eight people. It’s going to be devastating for them,” Mills predicted. “It is such a shock. It makes you question everything.”

The university plans to have support staff on duty this week to provide counseling to any students who feel they need someone to talk to.

Ryan, the district attorney, said Stryker was studying or doing work at a table in the Winchester Public Library’s reading room when Yao approached her shortly after 10:30 a.m. Saturday.

As other library patrons watched in horror, the man stabbed her again and again on her head, chest and torso.

Stryker died at a hospital a short while later.

Ryan said Yao is a resident of Winchester, a town of nearly 23,000 that is 9 miles northwest of Boston.

Neighbors of Yao interviewed by the Boston Herald said his behavior had become increasingly erratic in recent years. Some said they worried that he “will kill somebody” – and had shared those fears with police, The Washington Post reported.

One neighbor, a father of two young children who asked the Herald not to use his name, said Yao had tried to “smash our door down” in a 3 a.m. incident last year.

Leslie Luongo, another neighbor, told The Boston Globe that she would run to her car each day when she left for work at 5 a.m. because she was afraid of Yao.

She said that she wouldn’t let her children go outside whenever Yao was around and that people had started locking their doors and keeping bats by their beds.

Yao graduated from Winchester High School in 2012, according to the Globe. He ran cross country and wrestled, but classmates told the newspaper that his behavior became stranger in his last two years of school. He had stopped bathing, for example, and once posted an insensitive comment on Facebook about a classmate who had died.

Still, classmates told the paper, Yao’s behavior had never been violent.

The library’s director, Ann Wirtanen, announced in a statement posted on Facebook that the library will be closed “until at least Tuesday,” The Washington Post reported.