Zombie Apocalypse.

To your surprise, the group of people who distrust you dart off and open fire on you and your remaining buddies. You quickly leap behind some cover. Your acquaintances do the same, as well as return fire. It's all out war, but, unfortunately, you came relatively unprepared, with only a hand gun with a half clip of ammo left. You remain behind cover, yelling at your foes, trying to convince them to submit and come to their senses. You desperately try the peaceful route of reasoning, but soon discover that it's futile. You take aim and pick off your enemies with precision. The remaining party is weak and injured.