A man lying in the road was run over and killed today in Mount Vernon, according to authorities.

Police say the incident happened around 5 a.m. on Mount Vernon Avenue near Macquesten Parkway. They say the driver of an ambulette was coming up the hill and ran over a man lying in the middle of the road.

The driver did stop and stay at the scene.

Police tell News 12 they are looking at several possibilities such as the man was struck by another vehicle first and that driver left the scene, or he may have suffered some sort of medical problem that caused him to collapse in the road, or he may have been under the influence of drugs or alcohol and didn't realize what he was doing. "Detectives are on the scene; they're canvassing the area for witnesses and video, which we hope will help us with the events that occurred before the accident," says Mount Vernon Deputy Police Commissioner Shawn Harris.

The identity of the victim has not been released yet.

Mount Vernon Avenue is expected to be shut down for hours as police investigate.