I've seen people on youtube do it many times before, could be FinKone that i have watched but he or they can place the suspects in the cruiser without having to jump in, as if they are pushing a button to place the suspect in the car. I have not found any buttons for this yet. Anyone know what it could be?

When the suspect has been arrested, press E again while looking at them (a prompt should pop up in the upper left) and they will begin following you. Walk to your police car and press F, or whatever key you have to enter vehicles. Your officer should then walk to the back doors and open them, the suspect hops in, and you can then enter the car as a driver by pressing F again.

Aha okay thank you so much sir! :)