Al Qaeda is the bogeyman. When something bad like this happens, the media always start linking their name with it even if there is no evidence of their involvement. Remember how some media outlets were trying to blame AQ when that fascist nutter in Norway went on his killing spree?
The point is that we constantly have the threat of AQ rammed down our throats to keep us in fear. The terrorism isn't from AQ themselves, but from the fear of possible threats. It's in the interests of the establishment to keep it that way so that the public are more accepting in surrendering their civil liberties in return for being kept safe from the nasty-wasty terrorists - aka the bogeyman.
Anyway, going off topic a little. Like I said, I don't really want to discuss too much the possibility of AQ involvement until more facts are known.