SHARON (CBS) – The moment you hear the virtual alarm go off, it sends chills up your spine.

“It was a very realistic simulation,” said Dave Dudek of Sharon. He’s talking about a virtual reality active shooter drill, where a participant holds a training gun and fires imaginary bullets at a projector screen to stop a criminal.

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About 30 Sharon residents took part in the training on Wednesday night, the final step in their 10 days at the Citizens Academy through Sharon Police and Fire.

In the simulated experience, trainees are taught to try to deescalate situations and use their training to shoot when necessary. The simulation is run by a live operator, who changes the outcome based on the trainee’s behavior.

Active shooter training in Sharon (WBZ-TV)

Trainees step into a police officer’s shoes, deescalating domestic disputes and stopping armed robbers. “It raises your heart rate,” said Deputy Chief Don Brewer. “It’s very very nerve-wracking. It’s not like a video game where you just shoot everybody and you get points.”

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After the 20-seconds of high intensity simulation, there’s a debriefing period where trainees learn what they could have done better.

While every situation is intense, the moment the virtual school shooting appears on the screen, the mood in the room instantly shifts.

“All units report to Campus Middle Schools,” a fake scanner sounds. “There is an active shooting in progress.”

The trainees know it’s not real, but nonetheless, when they virtually “walk” the halls to look for the gunman, passing injured students and teachers on the ground, they take pause.

Dave Dudek has two children in school, and his wife is a teacher. He was visibly shaken both during and after the school shooting drills, which hit close to home given a mass shooting at a Colorado school just 24 hours prior. “The moment they talked about it being an active shooter scenario in a school setting,” he said, trailing off to gather himself. “I don’t even know how to put it to words. It started to affect me…It’s very frightening and scary, and I couldn’t help but think of my family.”

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The training is similar to training done by police officers for similar situations.

Kristina Rex