MINNEAPOLIS (WCCO) — It’s happened in small towns like Newtown, Connecticut, suburbs like Aurora, Colorado and as close as a small business in Bryn Mawr, Minnesota. The Minneapolis Police Department gave WCCO an exclusive look as its officers went through an intense training drill to stop an active shooter last week.

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We watched, as four cameras rolled, to see the lessons learned from other tragedies that police hope will save lives.

Cooper Elementary School is now closed. On this training day, it served as the classroom. The students are the 800-plus members of the Minneapolis Police Department.

“It’s a mass murder situation,” one officer said, as he pointed to a slideshow that explained the history of the active shooter scenario in the United States.

Sgt. Aaron Biard is the executive officer of the SWAT Unit.

“We don’t necessarily just contain a building and try to analyze what’s happening. We’re training to actually go in and end the situation,” Sgt. Biard said.

That situation is much different since we saw what happened at Columbine High School 14 years ago.

Officers stayed outside for close to an hour. When they finally went in the school, 15 were dead.

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“From this point on, everything changed for all of us,” Sgt. Biard said.

Departments are now taught to move in as soon as possible. Past shootings have taught them that four people die each minute an active shooter is on the loose.

Police responded to a real-life active shooter scene eight months ago in Minneapolis. Officers were on the scene at Accent Signage five minutes after the first call to 911. It was already too late.

After shooting and killing five people, police found the gunman dead in the basement. Half of all active-shooter cases end the same way, with the shooter’s suicide. Nearly as many are killed by police. Just a small fraction will surrender.

The drills start out slow. Soon, more stress is added through sounds and other obstacles to keep it unpredictable.

“This training is designed to be as realistic as possible,” Sgt. Biard said.

They practice, with the hope it won’t play out in real life, armed with the knowledge they’ll know what to do, if it does.

“That’s why we’re here,” Sgt. Biard said.

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The 850 members of the Minneapolis Police Department go through active shooter training every other year. Law enforcement from Newtown, Connecticut are scheduled to be in town to do more training with Minneapolis Police this summer to pass along what they learned after the tragedy at the elementary school.