Ok, I read somewhere on the forum that the "entering car" cannot be detected soon enough for receiving shotgun ammo from police cars and armor from SWAT trucks to be disabled, but I have another idea that might work. Here's the scenario.
Regular citizen enters a police car and receives a shotgun. He then exits the car and runs off.
Here is where the script should detect the exit of a Police Car when the player is not an officer, and automatically take 5 shotgun rounds away from the player.