The crash happened around 8:30 a.m. near mile marker 65.1 in Stafford.
Investigators say the trooper had stopped a vehicle.
That's when another car hit the trooper's vehicle, causing it to hit the car he stopped.
One of the cars caught fire, police say.
Two civilians involved in the crash were flown to Atlantic City Trauma Center.
The trooper was also taken to the hospital for minor injuries.