Nobody Wants to Die

Once you enter you first crime scene in the Green Tower, head to the back of the room and up the a set of stairs to the left. As you reach the next floor, there will be a desk in the middle and on this desk you will find some documents in labelled 'Top Secret'.

Pick them up with , and after a short bit of dialogue with Sara, you'll be given the option to either press to leave them or to burn them.

Press to leave the documents and once the scene ends the achievement will unlock. Now, hit and quit the game. Once you're back at the main menu, hit 'Continue' and repeat the steps above but choose to burn the documents and unlock the 'Firestarter' achievement.