Fired from Securitas for defending myself and bring sued ?

I was a Securitas security guard.  I attempted to ask a male transient under a cardboard box to leave.  He got up wanted to make excuses, use foul language.  I stood 15 feet from him.  I he came toward me running.  I took the company assigned flashlight and knocked him down. Securitas states I was wrong so therefore fired.  The transient no idea where he got the money but has a lawyer now to sue me.  Property management is being slow as releasing the video surveillance tapes of what happened.