It's WW2, and you are an american marine scout sniper. You and your spotter come across a situation where they are in close quarters with another sniper team, but these ones are Japanese. You are found, and have to fight for your life. You both engage and, let's say the enemy sniper is killed, but now your all out of ammo, save for one pistol bullet in the chamber. The Jap spotter uses his last grenade, and causes horrific damage to your spotter. His insides are spilling out, blood is being spat out of his mouth with every scream of absolute pain beyond belief. You reach for your pistol, and see the enemy taking out his knife, rushing towards you. So, here's your options: A) You shoot your friend in the head to end his agony. You will then be forced to engage in hand to hand combat with the enemy using your own knife, but there's only a 50% chance you will win. B) Shoot the enemy, with a 100% chance of killing him, so you live to fight another day. But your spotter will be forced to die extremely slowly, with no chance of survival.