WOBURN, Massachusetts -- A Massachusetts man charged with fatally stabbing a woman at a library during what prosecutors called an unprovoked attack has been held without bail.
Not guilty pleas to charges including murder were entered on behalf of 23-year-old Jeffrey Yao at his arraignment Monday.
Authorities say Yao stabbed 22-year-old Deane Stryker 20 times with a 10-inch hunting knife at the Winchester Public Library on Saturday. A prosecutor called it a "vicious, unprovoked attack."
Yao's lawyer says his client has "severe mental illness," which includes multiple hospitalizations.
Stryker was a student at the University of New England's College of Osteopathic Medicine who hoped to become a doctor.
Yao and Stryker attended Winchester High School at the same time, but it's unclear if they knew each other and the motive remains under investigation.
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Massachusetts man held without bail in 'unprovoked' fatal library stabbing