A woman working as a library security guard in Spring Valley was fatally stabbed following a confrontation with a patron, according to authorities.

Police say Blanchard Glaudin killed 52-year-old Sandra Wilson at the Finkelstein Memorial Library on Tuesday. Police say Wilson approached Glaudin who was listening to music with headphones and asked him to lower the volume. They say that’s when he stabbed her.

Wilson was transported to Good Samaritan Hospital where she died from her injuries, police say.

Glaudin, of Spring Valley, was charged with second-degree murder. He appeared in court the same day and entered a not guilty plea.

Prosecutors say Glaudin, who is 25 years old and a regular at the Finkelstein Memorial Library in Spring Valley, had a history of encounters with Wilson.

Glaudin has a previous violent arrest in Nyack, according to the District Attorney's office.

Law enforcement says Glaudin is believed to suffer from some form of mental illness.

Wilson's grieving family is questioning why the library did not have more safety precautions in place. Something as simple as a metal detector could have saved Wilson, her family says.

The Finkelstein Memorial Library was closed on Wednesday, according to its Facebook page.

Glaudin is expected to be back in court Monday.