They really couldn't figure out how Zhang Beixing had managed to beat that group of people into such a state with just one punch.
But if they didn't understand, how could Zhang Beixing, the person involved, not understand?
They could just go to the hospital and ask him. While they were at it, they could also check on his physical condition.
After discussing the human traffickers with Zhang Beixing, they would explain the police's handling of the situation and the reward they would provide him.
As for whether beating someone to death was illegal?
In theory, it was against the law. However, the other party consisted of human traffickers who had also wounded people with knives.
Zhang Beixing's actions were clearly self-defense, coupled with him acting bravely for a just cause. He might even be selected as an outstanding student representative of Shishi or something similar.
