I posed this question to my Israeli Orthodox Nationalist friend and my Chabad Rabbi. My friend emailed his response. The Rabbi and I discussed it verbally but his response was largely the same.
<<Shalom
I'm sorry to hear this and I hope you and your son are OK.
One of the principles of Judaism is that God rewards the righteous and punish the wicked, in this world and specially in the afterlife. However, we are not in the position of God to judge - meaning that this guy might had positive sides that we not aware of, but there were part of him and I'm sure God knows about them.
Another principle of Judaism is that there is option of Teshuva - repentance until the very last moment. Moreover, we assume that in the last moments every person makes Teshuva. The Rabis in the Talmud tells us that even a wicked man like king Pharaoh, just before drowning in the red sea, repentant for his evil dids.
I don't see any problem praying for this man. Praying for him doesn't justify his wrong doing (and trust me if he's doomed by God, your prayer won't help him much), it assumes that he had also positive sides and maybe in his last moments he repentant like Pharaoh did. Praying for him also effect you in a positive way and feeling sorry for his wasted life, connects you in in the right way life should be lived.
I plan to go to Shmary this shababt morning, might see you there
Shabat Shalom<<