From a City of Frederick press release:

The Frederick Police Department is urging residents to be vigilant as the 10th anniversary of 9-11 nears. After the death of Osama Bin Laden news reports indicated the recovery of plans by Al-Qaida to conduct attacks in the United States. We currently do not have any intelligence indicating plans for an attack in our area, but encourage that citizens observing any suspicious activity should immediately report it to the Frederick Police Department.

Be careful out there.