At about 9 a.m. Wednesday, Hinsdale Police Department dispatchers sent out a transmission stating Hinsdale Central High School reported a vehicle on fire in front of the building.

Upon arrival, emergency response units discovered something amiss inside the school as well: two “shooters” with guns were reportedly inside the school, threatening students and staff.

Within minutes a rapid response team from the Hinsdale Police Department arrived to set up a command center and deploy officers inside the building.

Shortly after, units from Darien, Burr Ridge, Downers Grove, Oak Brook and other adjoining communities arrived, many officers in Special Weapons And Tactics gear.

Within 15 minutes the faculty parking lot east of the school on Grant Street was filled with marked and unmarked police vehicles. Grant Street was closed south of 55th Street.

Entering the school in teams, the officers prepared for potential confrontations with unknown — and armed — assailants in a dangerous environment.

Within an hour both “shooters” were taken into custody, and the event ended.

The good news was the event was a pre-arranged training simulation that took six months to plan and just a few hours to execute.

“God forbid something like this could ever really happen, but we nothing beat hands-on training of this kind to simulate what could happen,” said Hinsdale Police Chief Bradley Bloom.

The training required the co-operation of Hinsdale Central High School staff and students.

Throughout the past few weeks, about 100 students were recruited for the exercise, and administrators worked closely with police and firefighters to stage a realistic simulation at the school, which is no longer in session.

Responding officers were unaware of specifics of the shooting scenario, said Deputy Police Chief Kevin Simpson, who organized the event.

Even though participating officers knew they were participating in a drill, hearing dispatchers over the radios heightened the anxiety of the responders.

“Officer down, 55th and Grant,” a woman’s voice crackled over the radio.

Moments later: “Shots fired in the hallway.”

At about 10 a.m.: “One suspect down, shot multiple times, in custody.”

Shortly after: “Subject down in a conference room.”

Within the next 30 minutes police had taken the second “suspect” into custody, then went through the normal procedures of securing the building and alerting school administrators the school was once again safe.

During the procedures the school went from a basic level called “shelter in place” to complete lock down, with classroom doors closed and windows covered.

Darien Police Chief Robert Pavelchik said the exercise was  valuable.

“Real-time, hands on training like this always beats sitting behind a desk watching a video,” Pavelchik said.

“Being there, hearing all the sounds, the dispatches, the smells, it really got the juices flowing even though you knew it was an exercise.”

Early in the exercise there was some confusion as some officers arriving on the scene were unsure what to do.

“It’s a lot better to learn from your mistakes now and correct them,” said Bloom. “There is no substitute for an exercise like this.”

Among areas discussed for future improvement were communication, tactics and command structure.

“The one thing we learned from the Columbine tragedy was that you need to get inside the building as quickly as possible,” Bloom said. “At Columbine, officers sealed off a perimeter and waited for a SWAT team to arrive. In this case, we were able to get a rapid response team inside the building immediately.”