Sarumane - Manga

The story takes place in a village in the 19th century. It begins when a group of hunters have just hunted a wild boar and see a monkey staring at them. A hunter threw stones at a monkey to chase it away. That night, the monkey and his friends went into the village and started attacking the people by imitating the human actions he saw, like stoning, butchering, abcxyz, etc.