The letter, which was distributed via an ad in the Washington Post, calls for a demilitarization of police forces, an effort to increase diversity, and the establishment of a "federal czar" to promote "the professionalization of local law enforcement."

"The proliferation of machine guns, silencers, armored vehicles and aircraft, and camouflage in local law enforcement units does not bode well for police-community relations, the future of our cities, or our country," the letter said.

Demilitarization advocates have already been calling for swift action in Washington, but this letter goes much further than what they were asking for.