As to teh specifics of this, and similar cases.
First. It has been my experience that even if you are the victim of an aggressor and you so much as push him back and he looses his balance falls down, hits his head on a lamp post or sidewalk and is knocked out or bleeding, the cop IS going to charge YOU with assault. Last man standing, especially if they are bigger physically, seems to get charged..no matter what.
In this case, reading between the lines... I wouldn't be surprised that once the homeowner saw.heard/confronted the intruder, he laid a real beating on the intruder. And he opened his mouth using lines like the tough-guy TERBites here have said like "Yeah, well he had it coming and he's lucky he didn'tget carried out in a body bag etc. Or some other words or actions that the homeowner/initial victiim decided to "teach him a lesson" or even saying he knew this guy and was pissed off and angry. Even having a baseball bat at yor front door if you don't play baseball shows your pre-meditated intention to use it as a weapon. Same with having a knife beside your bed. Or a baseball bat in 9our car when you don't play baseball.
Carrying a knife on your person is not illegal so long as your stated intention is to use it to cut twine, boxes or whatever. Once you say, or add, 'and just in case I get attacked I can defend myself', well then that makes it a prohibited weapon. If you happen to use it to defend yourself
Mens rea, aka guilty mind or intent makes all the difference.
If the guy had have said something like; "Well the guy came in and I yelled for him to leave, he didn't and came at me.. and I punched, kicked or pushed him down the stairs to defend myself... and that he got back up and kept coming at me... so I feared for my safety, and life that he may be on a PCP or otherwise mentally invulnerable to simple defense, so I hit him with whatever was close, (fire poker, whatever happened to be near) until he stopped moving SO THAT HE WAS NO LONGER A THREAT to me or my family", than he may very well not have been charged in the first place.
But if Bubba had have said' Yeah, I told the motha fucka to GTFO and he didn't so I taught himself some manners, or that he had a baseball bat beside his bed or front door and wnet looking for the guy and hit a home run as he came around the corner and hit a triple off his face, or worse, the back of his skull, .... well then he's gonna get convicted too.