Those Who Remain

To get the Rehabilitator Achievement you need to give the guy in the Police Car the keys. To find the keys, from where the police car is, head into the building and go straight to the far wall straight ahead of the entrance, there are lockers on your left and the keys and matches can be found in there.

The achievement will pop once you go through the door to exit the area.

This video will show how to get through to the end and includes full walkthrough for all achievements.

Rehabilitator Achievement 32:20