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This sure looks like military personnel training in military maneuvers, doesn't it?
It's the Massachusetts State Police fighting in the "Glock Mystery Challenge" at the Connecticut SWAT Challenge last year. Massachusetts residents will be either scared or comforted (or perhaps both) to know that the State Police won the overall competition last year, which included a variety of other shooting, busting up, smoke bombing and related events.
Note: various colored balloons and what looks like a public transport bus were harmed during the making of this video.