(WINCHESTER, Mass.) — A man attacked a woman from behind at a public library near Boston on Saturday and stabbed her repeatedly with a hunting knife, killing her and injuring an elderly man who came to her aid, authorities said. Middlesex District Attorney Marian Ryan said the 22-year-old woman was studying or doing work at a table in the Winchester Public Library’s reading room when 23-year-old Jeffrey Yao attacked her with a 10-inch knife.