This brief video shows a police helicopter circling between Porter Square and Harvard Square on Saturday night/Sunday morning April 18-19, 2009. Though the screen is almost all black, you can see the flashing red light and the white light from the helicopter. I saw this helicopter along Mass Avenue as I walked from the Porter Square Shopping Plaza toward Harvard Square. It was not a military helicopter. TV stations usually do not fly their copters at night unless there is a major event. This was police doing surveillance or looking for a suspect. It was likely a Bell bubble which state police use.