It happened on the westbound Southern State Parkway in Hempstead around 3 p.m.
The state trooper pulled over a vehicle near Exit 19S - Peninsula Boulevard. There was a struggle and when the trooper tried to arrest the driver, police say he took off with the trooper hanging from the window.
The Honda Accord coup then crashed into the center median.
That's when an Eyewitness News viewer started recording.
Watch the exclusive video here:
When the car finally came to a stop, the two men tumbled out of the gray Honda Accord, the trooper's face bloodied from the sudden assault, but still grappling with the driver. It was sudden and violent.
"He floored this car, you know the cruiser was right behind the suspect's car, and he literally just floored it with the cop hanging out, you literally see the cop's legs hanging out outside the vehicle," a witness said.
The commuter who shot the video didn't want to be identified, but by the time he started taking pictures, a woman was scrambling to get out of the car, and then the two men clearly struggled with each other, before the trooper finally got the upper hand and pulled the man to the median.
Two other motorists got out to help hold the suspect down as the trooper bent over to catch his breath.
"A couple Good Samaritans hopped out of their vehicles, when the officer got the guy, the suspect, out of the car, and as he tried to get him restrained, two Good Samaritans came out of their car and held the guy down," the witness said.
In time, police and other troopers showed up.
"It was like a movie. It was right in front of your face and you don't even believe it's happening," the witness said.
The trooper is being treated at a local hospital for head injuries.
Kelly is now facing charges of aggravated assault upon a police officer, second degree assault, reckless endangerment, resisting arrest, and obstructing governmental administration.
He's set to be arraigned on Thursday.
Any witnesses to this incident are asked to please contact the State Police at (631)756-3300. All calls will remain confidential.