BINGO! As soon as the defense brings up the much used in law enforcement "21 foot rule" the charges will be dropped.
The State was very quick in filing the manslaughter charge. That possibly indicates State investigators found some pretty solid evidence oearly on. Like talk of him threatening to shoot people before, a pattern of aggression, maybe even telling someone he wanted to shoot someone. None of these have anything to do with the actual self-defense but claiming self defense is quite difficult if the person was creating confrontations as a pretext to kill.