Irrelevant. He’s still evil and rotting in hell.
Not so. If you accept the existence of hell, heaven and God as he is portrayed in the Bible then you know that God can forgive sins, no matter how severe they may be. And He will do so for a true believer. Based on the testimony of the missionary mentioned, his acceptance of responsibility and remorse for the crimes he authored and acceptance of whatever punishment the court gave him (life without parole), I believe his transformation was genuine. One of the thieves who was crucified along with Jesus was saved by his remorse and his acceptance of Jesus as Lord as he was dying on the cross, despite his evil life up to that point. That God would do such a thing for someone who had lived an evil life shows how much He wants us to be with him eternally.
It also highlights the difference between fairness, which is a human concept, and justice, which is a divine concept. In all fairness, he should be rotting in hell. But God’s justice will be done and He will not send someone to hell if their transformation is genuine.