Casual listeners to 911 scanners Thursday morning may have been horrified to hear a tone-out for emergency responders to Redmond’s Ridgeview High School for a mass shooting. But the tennis players at the school and motorists passing by were nonplussed, having read the signs notifying them of police training in the area.

“Our officers knew they were going to be participating in a training today, but we didn’t let them know the details, because we wanted it to be as real-life as possible,” said Redmond Police Lt. Nathan Garibay. “At any moment we can turn a corner and something bad can happen; we need to be prepared to deal with that.”

Officers were checked — twice — to ensure none carried live rounds in their weapons as they arrived on scene, but otherwise they were told to respond to the drill as their training dictated. The exercise was a multiagency event, with law officers from Deschutes County, Oregon State Police, Black Butte, Sunriver and Bend. In addition, paramedics from Redmond Fire and Rescue, Black Butte and Bend responded to the tone-out, depicted to emergency responders as a shooter loose in a large high school.

Nearly 40 students and Ridgeview staff members helped with the training exercise. Some students were designated to play the role of injured victims, while others went through the scenario of protection by school staff and evacuation by police.

Because school is out for summer, the drill used the scenario of an incident occurring on a conference day when the building is lightly populated, said JB Demaris, director of support services for the Redmond School District.

“It was good for us to see how this might all work in a real-life situation, and staff told me they appreciated being able to understand what they might encounter in an actual intruder scenario,” he said.

The district began a building-by-building analysis of security weaknesses last winter, shortly after the Sandy Hook shooting, said Demaris. Most of the work to remedy those problems is complete, he added.

While the majority of the changes were physical alterations to buildings, some involved procedural modifications.

“Schools were not designed to have a high level of security in mind,” said Demaris.

Early observers of the exercise could see officers from multiple agencies surrounding the school, scanning windows and doors with automatic weapons at the ready. A group of students huddled in a deep swale in the parking lot, where they’d been evacuated and were under supervision by an officer.

A command center was set up on the far side of Ridge-view’s parking lot, as well as a staging area for paramedic crews and first aid.

“Command keeps in constant contact with the staging area if they are not in the same place and let’s them know when they are needed and it’s safe,” said Redmond Fire Marshal Traci Cooper.

Redmond police have not conducted a mass-casualty drill on this scale in the 10 years Garibay’s been with the department, but that’s going to change, he said.

“Officers in the region are very well trained, but what hasn’t happened before is putting them all together.”

From the original call-out just after 8 a.m. to arrival of first “victims” at the St. Charles Redmond emergency room around 9:30, the exercise was expected to take most of the morning, including debriefing with all of the participants.

“Good practitioners of anything should always be evaluating their performance and looking for improvement,” said Garibay, who coordinated the event. He used 12 evaluators during the drill, each charged with watching and evaluating a different aspect of the event, from evacuation of the building to the take-down of the shooter (a reserve Redmond officer) and patrol of the perimeter.

A chaplain was on site at the drill as well.

“There’s a whole other level to taking care of someone who’s been through something like this,” said Garibay. “We’re trying to cover all the bases.”

Debriefing everyone involved will take a while but Garibay’s first impression was a good one.

“I’m proud of all the responders; our tactics were solid, our coordination was good.”