This is a secret achievement.
Die while performing a stealth kill
This can can be done in chapter 2. Load up chapter 2 and once you are able to free the bird there should be 3 guys that you passed and others to get to the animal. Once you get over the big door to free it there will be a small cut scene. Once that is over, Get on top of the big door onto the ledge then hop down. One you can stealth kill, the other guy will hear you so stealth kill him and as you kill him the other guy at the far end in front of you will kill you as you do a stealth kill on his buddy.
If this doesn't work and if the two guys are standing next to each other run up or walk up and kill one of them and the other guy should kill you. If they happen to kill you after the fact you stealth kill one of them then just let them kill you and keep trying. Hope this method helps anyone out!