Making Du`a' for a person who has committed suicide

Q: I am a Sudanese Muslim. Thanks be to Allah, I work in the Kingdom of Saudi Arabia since a few years ago. Recently, I was informed that one of my relatives in Sudan has committed suicide - May Allah save us from that.I have sent a letter of condolence to his family in Sudan in which I invoked Allah to be merciful to him. I also sent another letter to a relative of mine who works in the United Arab Emirates to tell him of the event and of the letter I sent.He reproached me for offering condolences for a person who committed suicide and for invoking Allah to be merciful to him. Now the question which I want you to give me a clear answer for is as follows: Is it permissible to offer condolences to the family of a person who has committed suicide? Is it permissible to invoke Allah to be merciful to him? What is the substantiated legal evidence from the Qur'an and Sunnah?

(Part No. 9; Page No. 24)  A: It is unlawful for a Muslim to kill themselves; Allah (Exalted be He) says: ...and do not throw yourselves into destruction and: And do not kill yourselves (nor kill one another). Surely, Allâh is Most Merciful to you. And whoever commits that through aggression and injustice, We shall cast him into the Fire, and that is easy for Allâh. Also it is authentically reported that the Prophet (peace be upon him) said: He who kills himself with something, will be tormented with it on the Day of Resurrection. Narrated by Al-Bukhari, Muslim, and others. Whoever killed his self is a committer of a major sin and deserves Allah's torment. However, it is permissible for Muslims to invoke Allah to be merciful to him and to invoke Allah for him. It is also permissible to offer condolences to his family and relatives because he did not commit Kufr (disbelief) when he killed himself.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.