The Monster trying to help the little girl get her ball back is this from an adult's perspective. While he has the best intentions, all the crowd (including the girl's father) can see is him carrying her dangerously close to a precarious ledge.
The fact that he kills a man in the process for trying to interfere doesn't help. Specifically, he hits the poor fellow hard enough to cause him to go tumbling over the ledge. While we don't see the impact, we see the crowd's horrified reactions, and a conversation not very long after makes it explicit that the man is dead.
The same conversation mentions that the Monster killed two villagers, as opposed to just the one mentioned above. Previously, we had seen the Monster smack a guy in the face, causing him to fall out of frame. Just how hard did he hit him?
