UPDATE: The fine folks at the Sunlight Foundation managed to capture the whole thing on video. Take a look:

DCist reader Todd sent in this image of a large section of metal duct work that fell down on top of several parked cars this morning in an alley behind 1250 Connecticut Ave. NW (adjacent to 1800 N St. NW). The incident happened at about 10:30 a.m. Thankfully, no one was injured, but it’s scary to think what could have happened had someone been standing in the alley.

Workers are in the alley now disassembling and moving the vent. We’ve got a call in to the property manager to see if we can find out exactly how this happened.

Tom Lee contributed to this report