He doesn’t need to go through his life without knowing whether he shot someone. Like the jury, he can make a determination based on the facts without the luxury of absolute certainty.
There was plenty of evidence beyond the testimony of RG and LK.
He can admit to himself that he shot and nearly killed someone while delusional, or he can blame everyone else for his current circumstances — the judge, the jury, the police, the insurance companies as well as LK.
If he takes the latter route, as you (g) insist on doing, I think he’ll be committed for longer. Denial and blaming the Kanareks — and the police, the judge, the jury, etc is not helping him at this point.