Since 9/11 and this being a major public event with runners from around the world, it's reasonable to see the use of such dogs or even drills, no?
Or maybe there was a report of terror activity. Of course anything else could also be and we'd never be told about it.
“The power to declare war, including the power of judging the causes of war, is fully and exclusively vested in the legislature.” ~ James Madison, Father of the Constitution
“We do not believe in aggressive or preventive war. Such war is the weapon of dictators, not of free democratic countries like the United States.”~ Truman, Sept 1, 1950