Shouting "Fire!" isn't hate speech, it's basically a kind of social fraud: as a member of society, if you scream that some emergency is happening there is an expectation that such an emergency actually exists or could have been believed to exist. Especially in a case like this where the response is likely to injur people.

Free speech is about being able to state your oppinion. The person shouldn't "Fire!" in your example doesn't have the oppinion that there is a fire.