Rather a pity about 88, since I use it all the time as a sign-off in online chat sessions. It's a bilingual pun common among Chinese speakers. The Chinese word for 8 is pronounced ba, and so two 8s become ba-ba, or "bye-bye."

Guess I'll just have to switch to the variant 881, ba ba yi, also "bye bye."

The neo-Nazis have a whole string of these code signs.

Another sign is the 14 words that refers to an 88 word passage from Mein Kampf. They are frequently used together as 1488.

But I really don't think it likely that this particular nutjob has been waiting till he turned 88 to perform this attack. 9/11 was originally planned to be a week later which would have coincided with some event AQ considers significant. The Oklahoma City bomb was set a year after Waco.

Nut jobs might wait days, weeks or a year for a significant date, but not till they turn 88.