Another explanation (which might apply because he was an English major) comes from the novel Moby Dick. Ishmael is the only character who survives the sinking of the ship, and is the narrator of the story. It's been decades since I read that book, but it was full of allusions to the Bible and I do remember that it was pointed out in the class that Ishmael was an outcast.
It appears the “Ishmael” persona was clearly important to this sicko, since he used it as the return address on his mailing to NBC and was reported to have written “Ismail Ax” or “Ismael Ax” on his arm in red ink before committing his act. I have also read that it was his gamer ID on XBox Live, but have yet to see this point reported in the MSM.
I agree that the Ishmael literary possibility based on the Biblical allusion is interesting speculation:
http://www.freerepublic.com/focus/f-news/1819538/posts?page=910#910
This shows up both in Melville and in a book by an idiot named Quinn in which he uses a telepathic ape named Ishmael to spout leftist envirowacky drivel, around which I gather a mini-cult has developed (which is discussed by various posters in this thread), as well as other writers of course.
It was talked about from the beginning, when the writing on his arm was first disclosed, but that’s okay, MM; I do appreciate your posting, anyway. :-)