Law enforcement officials and other first responders participated in a full-scale exercise on April 26 designed to prepare for the possibility of a complex coordinated terror attack in the National Capital Region.

Area officials worked with the Metropolitan Washington Council of Governments (COG) to plan the exercise to help protect residents by preparing for an attack involving multiple target locations and teams of perpetrators.

The regional exercise was staged at six sites in the District of Columbia, suburban Maryland and Northern Virginia, and involved more than 700 police, fire, and emergency medical service personnel and volunteer actors. The locations included neighborhoods in the northeast and southeast quadrants of the District of Columbia, Prince George’s County, and Arlington and Fairfax Counties.  Residents in those neighborhoods were notified ahead of time to expect the exercise.

“Law enforcement officials practice and exercise their skills on their own regularly because that’s the best way to ensure we are always ready to respond quickly and professionally,” said Scott Boggs, COG Managing Director of Homeland Security and Public Safety before the exercise. “On April 26, we’ll go one step further and stage a very realistic emergency event involving multiple sites and actors posing as the casualties. However, there is no reason for residents to be alarmed because the exercise will occur in a controlled environment.”

Boggs told Newsweek that the exercise had been planned for close to a year, and was not a response to any current threat internationally. Rather, it was planned to address terror attacks such as what unfolded in 2015 in Paris.

MORE: Terrorism in America: U.S. Capital to hold terror attack drill with full-scale exercise (Newsweek)

MORE: Area first responders prepare for a ‘complex’ terror attack (WTOP)