An altercation over a bag ended in grisly fashion Monday, after a man was stabbed in the face in the restroom of the San Francisco Public Library's Main branch.

According to San Francisco Police Department spokesperson Officer Albie Esparza, the victim, described only as a 27-year-old man with no known address, was inside one of the library's restroom stalls at 4:40 p.m.. That's when he says that 38-year-old Louis Kessler burst into the stall, accused the victim of stealing his bag, and allegedly stabbed him in the face and head with a kitchen knife.

The Ex reports that the men had been arguing about the contested bag outside the library, which is located in the Civic Center area at 100 Larkin Street, earlier that day.

When the restroom attack began, Christian Klotz, one of the library's health and safety associates, "immediately jumped into it," library spokesperson Michelle Jeffers told the Ex.

"They heard a ruckus and he came running in."

Kessler was arrested by the SFPD officer stationed at the library, and was booked into jail on suspicion of attempted murder and false imprisonment, Esparza says.

The victim was transported to the hospital to be treated for his injuries, none of which are life-threatening, Esparza says.

Though the SFPL's main branch is known for occasional bizarre incidents from some of its more troubled clients, Jeffers tells the Ex that attacks like this one are rare.

“We don’t usually have assaults in the bathroom,” Jeffers says.

“We have sometimes behavior that violates our code of conduct but we don’t usually have any sorts of violent incidents."

Previously: Here's What You (Still) Can't Do In The Library: The SFPL Revises Their 'Code Of Conduct'