Waldo, having worked in executive protection and counter-terrorism, I can tell you that if someone is willing to die in an assassination attempt, they are likely to succeed. You CANNOT do more than take reasonable precautions.
Now is not the time to be placing blame, except on the persons who actually did the damage. This has the hallmarks of Osama bin Laden, but I'm going to wait until the facts are in.
This is going to get worse before it gets better. I would suggest that there are better things to do now other than blame people who were trying to prevent just this situation.