NATICK, Mass. (May 6, 2016) -- Shortly after 9 a.m. May 5, shots suddenly rang out inside Building 42 at Natick Soldier Systems Center.

A little more than an hour later, more gunfire erupted and an improvised explosive device was detonated in the north campus area of NSSC. In the aftermath of the two incidents, 11 people, including both of the attackers were dead, and 10 more were wounded.

Fortunately for all involved, rather than an actual terrorist attack, the incident was the installation's annual, full-scale exercise, designed to test the response of emergency personnel to such incidents.

The simulated attack began inside the building that houses the U.S. Army Research Institute of Environmental Medicine, when an active shooter killed four and wounded five other personnel. The shooter was killed minutes later by responding U.S. Army Garrison Natick Police, and the post went into lockdown.

"Control, be advised we have one shooter down," one USAG Natick officer reported over the radio. "All officers are good."

Town of Natick Police and Fire Departments and Fallon Ambulance Company personnel arrived to find role players with realistic wounds, who were taken to MetroWest Hospital.

In the next scenario on the other side of the installation, the second attacker opened fire and then set off the IED, which released hazardous materials. This action produced five dead and five wounded. The wounded were also removed from the scene and transported to MetroWest Hospital.

The second shooter then fled across the installation and attempted to escape by swimming across the choppy waters of Lake Cochituate on this cold, damp day. His body was later recovered by members of the Natick Dive Team.

In a pair of news conferences, USAG Natick Public Affairs personnel provided details to and took questions from the media, played by students from the Connecticut School of Broadcasting.

All of the exercise participants agreed that establishing and maintaining communications between the various organizations was critical.

"This exercise emphasized the importance of maintaining continuous relationships with the community throughout the year," said Lt. Col. Ryan Raymond, USAG Natick garrison commander. "As a commander, I can't overstate my appreciation for the longstanding support we receive from public and private agencies throughout the MetroWest region.

"This exercise and its critique are not intended to 'grade' ourselves. We're here to learn and improve; we can only do that if we are candid in our review."

Deputy Chief Victor Lipoma of the Natick Fire Department was in full agreement about the focus on communications.

"That's one of our toughest issues," Lipoma said. "We had a dive going on -- active shooter, EMS, (decontamination). Just trying to bring all those things together, experience-wise, that's huge."

Success begins with planning, said Lt. Brian Lauzon of the Natick Police Department.

"Getting everybody together around the same table to plan the exercise assists with the communications," Lauzon said. "Communications, obviously, is No. 1. But planning and (understanding) each other's craft and what their needs are, I think, is very, very important."

Dr. Kim Springer of the Office of the Chief Medical Examiner for Massachusetts said that her organization's priority is positively identifying the deceased in such incidents and reuniting them with their families as soon as possible.

"It's always important in (any event) that has more than one (deceased) person to make sure that the identity stays intact throughout and that we do our job as quickly and efficiently as we can," Springer said. "So, it's very important practice."

According to Jimmy Santoro, USAG Natick police chief, the installation must rely on a collaborative effort in emergencies.

"Without it, we can't exist," Santoro said. "We rely heavily on Natick because we're such a small installation. Our people have to learn their measures, and they need to learn how we operate.

"Every year, we learn something new. It's the only way to learn."