单独使用freak out

恩 惊呆了吓坏了紧张死了

This ordinary quiet guy just freaked out and shot ten people.
这个平时温和的家伙简直发疯了, 开枪打死了十个人.

She used to be the most correct person, but then suddenly last year she decided to freak out.
她曾经常是最合适的人选，可是去年她突然变得颓废起来。