Its a sad day. This attack was very cowardly. But it just shows that the US should take the threats it receives very seriously. They Al-Qaeda that Bin Laden heads up declared war on the US about 9 years ago when they bombed the WTC.
-WTC Bombing
-USS Cole Attack
-US Embassy Bombings in Africa
-WTC Plane Attacks
-Pentagon Plane Attacks
Its a shame that we rode so high on our horse. It has caused us a great amount of loss. Though not much can be done to protect against terrorists who are willing to die for their cause.
Bin Laden FBI Profile
Al-Qaeda
Text of Fatwah Urging Jihad Against Americans