Praise be to Allah.
We ask Allaah to compensate you for this tragedy and reward you for your patience. We have already discussed the issue of suicide in brief under question 373, section 5. As regards what you can do for your deceased loved one: if he was a Muslim who died without having done something that would put him beyond the pale of Islam (such as denying any part of the religion, making fun of some part of it, or totally neglecting Islam to the extent that he did not learn or do anything, etc.), then you can do many kinds of good deeds that may reach him (see question 763 for more details).
May Allaah take care of us and you by His Mercy.