Spoiler Alert! Only one guy survives.
Mark Wahlberg is an American Navy Seal on a dangerous mission in Afghanistan. He and his comrades are up on a mountain under such heavy fire that the only way they can survive is to jump off a cliff, bouncing off rocks and trees as they fall and roll hundreds of feet or more. Wahlberg lands on his butt right next to a rattling rattlesnake. (Rattlesnakes are always rattling in movies - it's the law. It looks like an Arizona Black Rattlesnake -which is native to where the film was shot in the mountains of New Mexico.) But he doesn't pull out his gun and kill it. He just rolls over away from it and we never see the snake again, as if he knows that there is no need to kill every rattlesnake you see. At that moment, the snake is the least of his worries. (Or maybe he knows that rattlesnakes are only found halfway around the world from Afghanistan.) Either way, kudos to the film for letting the snake alone.