I just heard on the radio that those were indeed DOD military exercises, designed to get the pilots accustomed to urban flying. There was a faint apology that they didn't give us more notice they were going to fill our airspace with war machines. Then they said that the exercises are going to continue, tonight. I am taking my camera to rowing class tonight. Not that such dark helicopters make great photographic subjects... but if they have the right to harass us with their presence, I can document the experience. Several women on my rowing crew said they were unnerved by the presence of the helicopters.
Me, I've had some experience with helicopters. When I was a ranger for the BLM in California, I had the opportunity to participate in a helicopter training with the Yosemite Rescue Squad and the California Highway Patrol. I got to be picked up off a mid-river rock on a helicopter, and discovered first hand that when you first make bodily contact with a running helicopter you are going to get shocked. I also was spotlighted by a search helicopter in Arizona once, when I was walking on an urban trail. A criminal had bailed out of a car on a nearby highway and hidden in the forest where I was walking, and the helicopter thought I might be the criminal. I went home immediately after that. Later that night a helicopter was flying around my building, shining lights into the windows. The ground forces never came, though I half expected to be searched just because I was walking in the forest after dark.
To me, helicopters symbolize the ultimate power of the government to exert intimidating control over regular citizens. No matter how you travel, they can follow you. No matter what you do, they can find you. Helicopters make me uneasy.