A Stern Lecture?

Friday night, I was up to my favorite activity, shredding paper in the basement, when I heard sharp commands from the parking to lay face down. Looking out the back gate, I could see a cop car, and a cop issuing orders to three young men. There were several others present too, and I wondered whether a chained portion of the DMV lot had been intruded upon by someone.

Soon, there were four cop cars there. The police made the three people lie prone, face down, for an hour. Then they allowed them to sit on the pavement while the police delivered what sounded like a stern lecture. Then with an enormous flourish of sirens and lights, three of the cars raced away, leaving just the original cop car. Then, that cop released the three people, and they walked away. But the reason for it all is still a mystery....