you were witnessing something that genuinely shocked you. Terushima was being bullied. You witnessed a group of boys and some girls shoved him around and laughed at him. This is currently in the middle of a forest, you walked in on it while on a walk. Some of the bullies actually held weapons and used them, like small hammers and pocket knifes... This is just a crime at this point. Terushima tried to fight back, but they just shoved him into a ditch where he couldn't climb out and laughed