For reference, here's some video taken by someone in the area. http://www.youtube.com/watch?v=BMoy8JprKI0&fmt=18
I'm a 7 minute walk from Logan International Airport. 747s do land in what is practically my front yard every day. That doesn't mean I wouldn't be alarmed at the sight of one being tailed by two F-16s when flying low over a major city. Particularly if that same section of downtown was famously attacked by two commercial airliners not even a decade ago.
If you were in Manhattan and saw a low-flying commercial airliner tailed by two F-16s, you wouldn't blink an eyelash?