Residents of lower Manhattan in New York City got a bit of a scare recently as MH-60 Black Hawk and MH-6 Little Bird helicopters from the U.S. Army’s elite 160th Special Operations Aviation Regiment went zooming between skyscrapers as part of a training exercise. But it’s hardly the first time the U.S. military, and the Night Stalkers in particular, have caused a stir with similar so-called “realistic urban training” events, or RUTs.

This particular exercise occurred overnight on April 17-18, 2018 and involved at least two MH-60s and two MH-6s, likely carrying additional special operators. According to witnesses, there may have been two additional MH-6 helicopters as well. A subsequent statement from the New York Police Department said that the activities would be confined to areas around the Verrazano and Brooklyn Bridges, as well as near Ellis Island and the Statue of Liberty.

The helicopters flew low enough to pass right by peoples’ apartments, rattlingly windows and otherwise causing everything to shake. “Didn’t see them but my whole apartment shook and we hit the floor,” one of many concerned citizens posted on Twitter. So far, there is no additional information about what specific “targets” the special operations forces assaulted or the exercise’s overall scenario.

There were also reports that a Staten Island Ferry went sailing down the Hudson River flanked by police boats. It is possible that the special operators rappelled onto the vessel in response to a mock terrorist attack or hostage scenario.

In addition, the day before the apparent main event, a U.S. Air Force Special Operations Command U-28A spy plane was also spotted on online flight tracking software orbiting in the same general area. This single-engine aircraft, which carries electro-optical and infrared video cameras and signals intelligence systems, was likely conducting a mock intelligence, surveillance, and reconnaissance mission ahead of the simulated raid itself.