Fox 5 backtracked on the "packages" report. All they are committing to now is that three men of middle-eastern descent were detained after suspicious activity on the bridge.
There have been specific threats to the Brooklyn Bridge in the past. Never heard of threats to the Williamsburg; but I should note that the neighborhood called Williamsburg, in Brooklyn that is adjacent to the Williamsburg Bridge, is heavily Orthodox Jewish.
There have been reports in the media in recent months that the 9/11 terrorists originally had planned to hit the neighborhood of Williamsburg, instead of the WTC, because the original goal had been to kill as many Jews as possible.
My son used to live pretty close to the foot of the bridge in Brooklyn. Actually it's a very divers neighborhood, and there are a lot of Muslims there. I believe it is close to the mosque that got busted for illegal donations recently.
On the Manhattan side it is not too far from Wall Street.