Sahih Muslim Book 54, Hadith 22
The last Hour will not come until the two parties (of Muslims) confront each other and there is a large-scale massacre amongst them and the claim of both of them is the same.
When two Muslims (confront each other) and the one amongst them attacks his brother with a weapon, both of them are at the brink of Hell-Fire. And when one of them kills his companion, both of them get into Hell-Fire.
The last Hour will not come unless there is much bloodshed. They said: What is harj? Thereupon he said: Bloodshed. bloodshed.