Hi Pappy,
For what is worth (which I know is always a hollow statement coming from a stranger) you have my deepest sympathy, and my heart goes out to the pain you suffered, I know how the loss of my nephew affected my brother 17 years ago, and he has never really recovered from it. So I do hope and pray that God continues bring you through this and continues to heal and restore your broken heart, and lets you know His constant Presence and saving Hand on your life, holding you, grieving with you, and reading to bear this terrible burden.
As to the question at hand, well first off no one is in 'hell' right now, the final judgement will occur at the end of this age, and I first off believe the statement that God judges people by the light is to be taken as a positive statement, meaning that those who have been faithful to that will be brought by the resurrection to see that Jesus what the Truth they were seeking, and will see and embrace the target of the faith. But your son seems to have had a faith in the Lord, so my opinion is he is fine, and is resting with Jesus awaiting the resurrection, after all your son was suffering it seems from depression and many afflictions and pressures that this age brings and hurts people with. He was hardly thinking in a clear and rational way in his choices, and wasn't able to see a way out of his situation, the enemy filling his mind with deceptions. So his was hardly a either a clear decision, or at any time during it was he rejecting Jesus, His life and freeing rule, he was terribly deceived and confused at the time, after all, if one of us in depression lashed out at someone in anger and suddenly got killed would we be then damned because we didn't confess that one sin O_O ? That's crazy, even more, well all have sin, and the one who says he doesn't is a liar and the truth isn't in him, so God is continually at work, to repair and renew us in a work that will only be completed at the resurrection, only then will be be free of sin and fully the human being God intended us to be. So this logic would see us all damned O_O, but that is, thank God (and I mean that with every fibre of my being), not true, rather that verdict is brought forward when we believe on Him and the declaring that we are justified that we will hear then is brought forward from that future into the present, and we know we are free. When Jesus said 'It is finished!' in victory, it is finished, sin and evil has no hold on us, and has no hold on your son, God will bring through this, and will delver him from this evil just like He will deliver us from our sins and evil, they are not great then God. And this one act can and will not defeat God's hold on your son, and will not defeat His love for you son, He will bring Him through this, and you will seem him again.
I truly hope God brings you peace, and shines his love in your heart, be blessed and I hope your heart and life sees His love more and more. Sometimes the cross we have to bear is truly a hard one, but He enables us, and He carries it with us.
God bless and take care
(also, I won't respond to others on this issue, I understand many will disagree with me, but no something like this, I don't wish to enter into debates with, as my feelings would run high, and I do wish to always be loving towards my brothers and sister in the Messiah, so God bless you even though we disagree and let us just bear with each other).