Patrons at a Rockland County library helped detain a suspect Tuesday who stabbed a female security guard to death in a vicious attack, reports said.

The suspect approached the victim, a 52-year-old woman who works on the third floor of Finkelstein Memorial Library, at about 2 p.m. and plunged a knife into her, WNBC reported.

Officers with the Spring Valley Police Department arrived at the library a short while later and found patrons holding down the 25-year-old suspect, reports said.

“He ran towards the exit, but a group of people subdued him at the door,” witness Luis Velasquez told Lohud. “It was really one person who first grabbed him, but then other people restrained him, too. Everything happened really fast.”

The victim was taken to Good Samaritan Hospital, where she died, WNBC reported.

“A terrible act of violence today at a library many in our community visit,” State Sen. David Carlucci posted on Twitter. “Very disheartened to read that a woman was stabbed at the Finkelstein Memorial Library in Spring Valley.”

The library announced an emergency closing on its Facebook page for 2:45 p.m. and later posted that it would remain closed on Wednesday.