Besides it being against the law and a reportable offense for him to threaten you or get violent with you, it is against the law for him to harass you by getting you detained for psychiatric observation when it isn't warranted. He did that once. If he does it again, he establishes a pattern of harassment and you can take legal steps against him for that too. Besides, the authorities will get to know him and that he has that pattern of retaliating against you that way, and they will know that he is just trying to harass you again and will put a stop to it.