Why would AM introduce trying to commit suicide as a reason for the latest incident, just to debunk it. What is the context? It feels like he was offering information that wouldn't have initially been assumed.
To me this makes the event seem even more suspicious, and even more likely to be a botched suicide, staged after the fact to be a drive-by attack by unknown persons.
After listening to the 911 call snippets, I agree that it does sound like he's admonishing (the now deceased) Paul for getting involved in some way. It might be worth trying to clean up the audio to see if there's any other unguarded comments being made in the background.
Bear in mind that this is only speculation, but now I am leaning towards the theory that AM intended to kill his wife. Perhaps she had found out about the embezzlement and was threatening to go public, or had had enough of his drug addiction, or was threatening a costly divorce and the airing out of the family's dirty laundry.
He uses an assault rifle and perhaps a pretext to get her to come outside. He is not expecting Paul to be there, though. Paul hears the shots and comes running outside to investigate, carrying the shotgun with him. He is shocked to come upon his own father who manages to talk him down and to give him the shotgun. AM turns the shotgun on his son, fearful that the truth might come out if he doesn't kill him too. That would explain him being upset that Paul got involved. An unintended victim, collateral damage.
