Payback.

He was looking for a weapon when he stumbled upon a loot box. He didn't even consider the result of his actions because he didn't sense any danger. He broke the loot box and found a very strong blade. Some people saw him get the weapon and they attacked him. He could have avoided them if only he had been careful and observant of his surroundings. He could have hidden and waited for them to pass by before breaking the loot box but he didn't because he didn't sense any danger.

He was wrong about that. His new instinct for danger gave him false confidence. The box wasn't dangerous but the 10 or so people that attacked him are very dangerous. He fought them but they were too many for him. So he ran away from them and they gave chase. He was able to escape due to his superior speed and he found a place to hide in the city of stone that they are in.