First responders found themselves faced with a scary but increasingly all too familiar scene on Wednesday.

"One female down. Extricate via stretcher," were the words blurted from an emergency radio.

"I heard gunshots, saw the shooter with rifle come out of the classroom," Mike Wagner said.

"Local police came in and actually shot the shooter," said Kristen Miller.

Dozens were injured. A frantic search was conducted for several shooters. A school was put on lockdown.

Amidst all the cops, chaos, and confusion was good news. It wasn't a real emergency; it was a drill set up by the Parkland School District in Lehigh County.

Some 300 volunteers and more than a dozen police agencies turned the district's high school into the scene of an emergency response simulation. It's a plan that had been in the works since last fall.

"It was very, very scary. A very realistic sound system in there," Lewis said.

"Especially when heard blank gun shots going off," Wagner explained.

Reality was what police were aiming for, with fake blood on the floor, simulated shooting victims on the ground and a medical helicopter in the sky.

"While it looks like organized chaos, everyone knows what they are doing, and they perform it," said the drill's coordinator, Robert Werts, of the Northeast Pennsylvania Counter Terrorism Task Force.

Procedures practiced during the shooting at Columbine High School in Colorado more than decade ago of sitting and waiting are over.

"Once two or three police officers are together, we neutralize those shooters the best they can," Wertz explained.

It's not just police officers who were being trained Wednesday. The school district was on alert, too.

Nicole McGalla, Parkland's director of communications, updated a fake website, which in a real-life situation, would give parents the latest information and directions of what to do.

"While we practice fire drills, practice lock down drills, not the same as a simulated exercise," McGalla said.

You never want something like this to actually happen, but those who took part in the exercise will now know how to react and respond if it does.