Hold on now. I read the page you’re quoting. Here is what it said:
Forty Massachusetts National Guardsmen, supported by a helicopter, and approved directly by the Pentagon, searched the patrons at a Grateful Dead concert in Foxboro and fingered over a hundred people for the police. Forty arrests were made.
Nowhere does it say that they flew the helicopters above the concert. It’d be a heck of a bad way to learn anything that’s going on — Huey's are loud. To get close enough to see, you’d also have the issue of downdraft. Being supported by a helicopter does not mean you’re flying around in it. Also, this wasn’t Massachusetts police, it was the national guard, working under the auspices of the Pentagon.
Read your sources better. Massachusetts police did not fly the helicopters, and it doesn’t say that they flew over the concert.