News 12 has obtained surveillance video appearing to show the moments leading to a stabbing of a custodian during a robbery in Mount Vernon Tuesday.

Police say Edward Williams Elementary School custodian Derek Fox, 44, was stabbed in the back and arm while on his lunch break near the Boys and Girls Club of Mount Vernon on West Fifth Street just after 1:30 p.m.

Th video shows a man in white standing on the corner. He then begins to follow Fox as he walks by.

Investigators tell News 12 the suspect approached Fox, demanded money and stabbed Fox when he refused.

Fox ran up the street to a bodega for help. Officers arrived quickly and took Fox to Jacobi Medical Center in the Bronx where he was stabilized. He is expected to recover from his injuries.

The Williams School was placed into a heightened state of security, and the nearby Cecil H. Parker Elementary School was placed on lockout because of how close the incident was to the campus.

The incident shocked both faculty and students' parents.

"It's anxiety-triggering just to know what's going on. It's like a trend now, and I'm not sure what safety precautions they have, but something has to change," said parent Natalee Campbell.

"We're hoping he recovers quickly," said Mount Vernon acting school Superintendent Dr. K. Veronica Smith.

Edwin Lopez, the director of safety and security at the Boys and Girls Club of Mount Vernon, says there was a ceremony held in front of their building just last week to plant a tree and now a man was violently attacked in the same spot. "At that time, we didn't have kids in the building, thank God, but just to see that happen in broad daylight is what's scary," says Lopez.

Police say they are still searching for the suspect. They are asking anyone with information to call them at 914-665-2300 or text their message/tip to 847411 (TIP411).