Thanks for the question.
While suicide is a mortal sin, and mortal sins are damnable, we cannot be certain that God has judged this individual as responsible or not.
Only God knows the circumstances of the event, and the state of his soul. What we can do is pray and make sacrifices for the soul of the departed.
can be of great benefit for him — for even though this happened in the past, there is no past for God.
He can see our actions now and the event of the suicide simultaneously so your actions could incur grace that can be applied to his soul, and perhaps even a conversion or repentance in the moment of critical necessity. We can make a difference for those who are in the Hands of God and need His Mercy. So, if you want mercy for your friend, give God something to apply to his soul and he will pour out His Mercy.
Lastly, the depth of Hell is relative to the punishment deserved by the sinner. The worst unrepentant sins incur the greatest wrath and therefore the souls with these offenses are the worst off. No one should ever suffer the fate of Hell, but too many do so we must plea for mercy for them and ourselves, lest we also turn away from the right way.
Keep your focus on God's Mercy and entrust your friend to the Merciful Heart of Jesus; He never disappoints.