Since people are already speaking about magic which pretty far from reality why do you need to stick to the accident related guro?

There are way more possibilities.

various insanity related situations:

Yandere girl who decides to commit mutual suicide together with her love.
Or feeding pieces of herself to the boy and later eating him.

Strange beliefs that make people mutilate or kill other people and themselves.

drugs or viruses that alter brain functions. (Actually happens in real life pretty often.)


Complete surrealism where nothing makes sense at all:

overexaggerated executions and punishments maybe for getting F at school or because of some game bet.

casual mutilations and deaths with messed up motivations and responses.

story based surrealism is advantageous because you can conveniently forget what happened before. while picture based surrelism is great because it is hard to explain totall nonsese in form of text.