Lightly, no! Graciously, that depends on the person themselves and God. Only God knows if he repented before he actually died or not, we don't. One of the thieves on the cross gave every appearance of being headed for hell up until the point where he realized just how different Jesus' crucifixion was from theirs. Then he started defending Jesus, and asked Jesus to remember him when Jesus came into His Kingdom. Jesus responded, "Truly, I say To you, Today you will be with Me in Paradise." I would be firm with those who are about to commit suicide, and warn them there is no turning back from a decision like that, and they need to think about the people left behind, I would also remind them that murder (even if self-murder) is a grave sin against God and they are not to presume upon grace being extended in that circumstance...