The phrase is: to go psycho on someone. It is another way to say "go crazy on someone." It can mean anything from a person yelling at someone or a person throwing things at someone. It comes from the word "psychotic." If your friend has a fight with her boyfriend for example, she might say, "He went psycho on me when I told him I wanted to break up." Another way to say it would be, "He reacted like a crazy person when I told him I wanted to break up."