He's a kid that killed two people, even though they were dirt-bags, it's got to eat at him.
I don't know how I would react if I had to kill someone, but I doubt I would be cheerful about it - even if it was self-defense. Just damn.
It is obvious from trial footage that the battle took a toll on him. I hope he is getting counseling to remind him that it was not his fault and that he should embrace the skill and courage with which he fought.
His rifle could be a symbol of the will to resist the evil that is overtaking this country.