I'm so sorry. I'm sure you will find a better job with better people. ☺

Dude you never fire someone day one. Always at least clear it with the higher ups. Or even better, file a report with the police. Ydi

Tell them the whole story, and say "He was physically abusing a co-worker/boss. If he had punched anyone else, I would have still fired him. He was creating a hostile work environment and that is NOT ok. And what would you do if he punched you? Just let him get away with it?"

This needs a follow up

How is firing someone who punched you abusing your power?

Pretty sure firing an employee for assaulting you is totally reasonable. Get HR involved, that's bullshit.

Here is the real question. Did you actually have the authority to fire him? The fact that you were promoted to the management team does not automatically mean you have the authority to terminate someones employment. For example, and no one leap on me because I'm not saying this is exactly how the OP's company works this is purely an example of how management teams can be set up, the management "team" could consist of something like a Team leader, Floor manager, Department head, Area Manager, and the Companies Owner. Now in those situations the Team Leader usually has the authority to write people up, suspend them, and add notes into their file but that's it. They are still a Manager, they are still above others but they don't have the authority to fire anyone. That usually falls to the Head of the Department. Is it possible that what happened here is that you were essentially a Team Leader but you attempted to use the Authority of a Department Head and that's why they said you were "abusing" your power?

I made an account just to reply to this post. and how dare they, human resources won't help you, they just fired you dummy. and they work for the company. go to your local eeco (equal opportunity employment commission) a federally funded organization. and go to the ACLU. DONT LET THOSE ***** **** YOU OVER. VIVA LA REVOLUTION

please do a follow up

I think you should and better fight this.