He was charged with aggravated assault and the intruder was airlifted with life threatening injuries. This will come down to whether the force he was was lawful, including if it was ‘reasonable’ and ‘necessary’. The law does not expect force used in self defence to be measured with exactitude.
I don’t want to speculate about an active criminal case. I would infer from the charges that police believe the force used by the recent and the injury that resulted exceeded what the law can support. It’ll probably be quite a while before we get much of an idea of just what went down in that apartment.