NATICK, Mass. (May 8, 2013) -- As U.S. Army Garrison Natick police and security personnel entered the Prendergast Building, they saw one man shoot another. They ended the threat by firing, taking down the subject with a single shot.

When they continued to the building's second floor, they discovered another subject with a knife holding a hostage. They backed off and called a SWAT team and trained hostage negotiators.

Fortunately, the May 8 incident was part of a two-day antiterrorism/emergency management exercise at Natick that also involved local police and other first responders.

"In any sort of incident, it's going to be hand in hand with local partners," said Lt. Col. Frank Sobchak, USAG-Natick garrison commander. "So having the Natick police here is hugely beneficial to the scenario. We really couldn't do it without them."

Lt. Steven Pagliarulo of the Natick Police Department said that the exercise also served an important purpose for his officers.

"It's imperative that we train together and become familiar with each other's protocols," Pagliarulo said. "Also, we want our officers to be familiar with the base itself. Some of our newer officers have never been here, so it's important to have face-to-face contact."

Pagliarulo added that the recent Boston Marathon bombings had emphasized the importance of cooperation between different agencies.

"Also, we exercise communications," Pagliarulo said. "That's probably one of the key factors in something like this, is establishing communications."

Officer Scott Woodward of the USAG-Natick police, part of the "contact" team that originally entered the building, agreed that working with local police has been a benefit.

"We've been integrating training with them," Woodward said. "It inspires confidence in all of the players, because they know that we're all on the same page. We use the same doctrine, the same language, the same responses."

The use of simulated munitions -- like paintballs -- that travel 450 feet per second added an element of realism to the scenario. Participants wore head and throat protection as safety precautions.

"Basically, it's a 9-millimeter round, but it's got a plastic tip," said Lt. David McCrillis of the USAG-Natick police. "Inside of that tip is basically detergent.

"If you got hit, it would be equivalent to … getting a bee sting … or getting shot with a BB gun. The suspects only have red in their weapons, and the officers have blue."

The change from active shooter to a hostage situation was meant to test the response of garrison and town police.

"The reason we do that is we want to see if they switch gears," said McCrillis of the officers, who did just that.

"We changed doctrine at that point," Woodward said. "There's no reason to rush in. So then we just changed gears, and then we tried to contain it."

The scenario just reinforced what these first responders already knew.

"You can't just go rushing in madly," said Woodward, "but you do have to do it with urgency and just hope that your training kicks in."