HOLTSVILLE, N.Y. (CBSNewYork)– A patient suffering from a mental illness was struck and killed by a car after he jumped out of the back of a moving ambulance on Long Island, police said.

Now police are searching for the hit and run driver.

It happened just before 7 p.m. Monday in Holstville as Frank Ligrnetta, 51, of Bay Shore was being transported from Stony Brook University Hospital to a facility in Amityville.

“I would really like to know what happened, but I don’t know where to start,” Michael Cambridge, a friend of the victim, told CBS2’s Jennifer McLogan.

As the ambulance headed south on Nicolls Road, police said Ligrnetta got out of his stretcher and jumped out of the vehicle.

“He was strapped into the stretcher, he unbuckled himself and opened the back door of the ambulance himself and exited,” Suffolk County Deputy Police Commissioner Tim Sini said.

The victim was in the back of the ambulance with an attendant, but there was no struggle, according to Sini. Ligrnetta was then struck by a dark-colored sedan, which fled the scene.

Ligrnetta was pronounced dead at the scene.

Friends of the Bay Shore victim said there were troubling signs before the accident. They said police had to forcibly open his front door after his sister called 911 regarding concerns about her brother’s mental and physical health.

The apartment manager and neighbors say Ligrnetta’s downward spiral was sudden.

“He was like the mayor, he knew everybody here,” Nancy Elliott, another one of the victim’s neighbors, said.

Elliott can’t fathom the fact that the driver fled the scene.

“It is always best to tell the truth. If you did something wrong, stop and take care of it, don’t do that, he is a person,” she said.

The ambulance company is reluctant to speak, but police say the driver and attendant appeared to have followed procedure.

Police are investigating how fast the ambulance was going when the incident occurred.

Anyone with information about the incident is asked to call the Vehicular Crime Unit at 631-852-6555 or call anonymously to Crime Stoppers at 1-800-220-TIPS.