By Jim Smith

WINCHESTER (CBS) – A woman was fatally stabbed and an elderly man injured rushing to her aide inside Winchester Public Library on Saturday.

Just before 11 a.m. the 22-year-old woman was sitting at a table when police say 23-year-old Jeffrey Yao attacked and stabbed her with a 10-inch hunting knife.

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Police investigate a double stabbing inside Winchester Public Library. (Image Credit/Ryan Bernat/WBZ-TV)

A 77-year-old man rushed in to help the woman and was also stabbed in the arm. He is expected to survive.

“The young woman was in the library, seated at a table, in one of the reading rooms apparently studying or doing some work (when) Mr. Yao began striking her with what we now know to be, appears to be, a hunting knife, with approximately a 10-inch blade,” Middlesex District Attorney Marian Ryan said to reporters. “She suffered a number of slash and stab wounds.”

Winchester Library stabbing suspect Jeffrey Yao. (Image Credit: Winchester Police)

In a statement, Winchester Public Library Director Ann Wirtanen said the library will be closed until at least Tuesday.

“The staff and Board of Trustees are deeply saddened by the tragic event which occurred this morning at the library,” Wirtanen said. “Our thoughts are with the young woman’s family and those who were injured and deeply traumatized.  We are doing everything we can to cooperate with the investigation and will remain closed until at least Tuesday.”

Winchester Schools Superintendent Judith Evans said in a statement that the community is grieving the sudden loss of the murder victim.

“We grieve for her, her family, and friends as we struggle to understand and process this terrible and shocking loss for our community,” Evans said. “Our hearts are with all those involved, especially those who witnessed the event and tried to assist.”

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Evans said high school staff and administrators will meet with district’s Incident Management Team to develop a plan to offer support to the students, families, and staff members when school opens on Monday after the vacation week.

“Our teachers and administrators appreciate your support and understanding as we anticipate that the return to school may be quite difficult for some members of our school community,” Evans said.

The murder stunned library patrons, who saw several police cruisers and an ambulance rush to the scene.

“There was a woman taken out and I didn’t get close to her but it appeared that she had some injury to the shoulder,” Russ Ganz said.

As far as motive goes, police aren’t saying if Yao knew the victim or not. The suspect lived with his parents a few miles away. Neighbors said he appears to have mental issues.

“You kinda knew this kid was a ticking time bomb. Last August, he tried to throw a potted plant through the window over there. He ran from the police and they took him into custody and they said he was off his medication,” Nicole Luongo said.

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Yao, who was known to police before the stabbing, is expected to be arraigned Monday on murder charges.