WINCHESTER (CBS) – Winchester Police and grief counselors were at the public library as it re-opened Tuesday afternoon, three days after a young woman was brutally murdered there.

Jeffrey Yao, 23, is being held without bail after pleading not guilty Monday to charges of murder and armed assault with intent to murder.

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Jeffrey Yao in Woburn District Court, February 26, 2018. (WBZ-TV)

Investigators say he was not provoked when he approached 22-year-old Deane Stryker from behind Saturday as she studied inside the library and stabbed her 20 times with a 10-inch hunting knife.

Deane Kenny Stryker (Photo credit: University of New England)

Several people tried to stop Yao, including 77-year-old Lester Taber, who was reading a newspaper before the attack and also ended up getting stabbed.

Lester Taber. (WBZ-TV)

Stryker died.  She was a first-year student at the University of New England’s College of Osteopathic Medicine and hoped to eventually become a doctor. She and Yao both graduated from Winchester High School.

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Yao’s attorney, J.W. Carney, said Yao did not know Stryker and said his client is a very troubled man with a history of mental illness.

The Winchester Public Library. (WBZ-TV)

Several people have left flowers outside the library and others have drawn hearts with chalk on the sidewalk to honor Stryker.

The entrance to the Winchester Public Library on Tuesday. (WBZ-TV)

Speaking to reporters Tuesday, library director Ann Wirtanen had enormous praise for Taber, who is a frequent visitor at the library.

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“He was absolutely heroic.  For him to step in, in an instant, when so many people are frozen, you don’t understand what’s happening at the moment and he stepped in.  What a man, What a man,” she said.