Hindsight is easy. I don’t believe it’s likely that you can surmise what you “would have done” “if you had been there”.
It's actually very easy. I would not allow a 19 year old, depressed, suicidal, mentally ill boy .. who had been convicted of a felony and known to make death threats, to bring an AK-47 into my house.
Is there something wrong with that logic? Just what is it about that statement, that you find so hard to believe? What would you have done?