Was that the president?

I forgot a major part of the day and William keeps mentioning it. We think, emphasize "think", that we may have seen the president go by. While waiting in line for tickets to the Washington Monument, we heard a bunch of sirens. Then about 4-5 police motorcycles go by, along with 2-3 police cars, 2 limos, and a few black suburbans. William tried to take a picture, but there were a few tress in the way. We heard somebody else say they thought it was the president too. Whoever it was though, was a lot more important than us apparently!