For months after the shooting, as the coordinator for the team that deals with active shooters, Branden routinely worked long hours to talk to churches and school groups, casinos and small businesses about preparing for future shootings. He was surprised with the intensity of the task.

“It was even more aggressive than anything I was doing before — like constant long days and nights,” Branden said. “I’ve heard people talk about working 13- and 14-hour days and I think how can they do that. But I just did. It was like passion that came to get something done.”

He has taught his own children to “run, hide or fight,” and facilitated dozens of “stop the bleeding” trainings. He gets frustrated when someone suggests such training is unnecessary. If it wasn’t, he argues, people would not hesitate when they hear a series of loud pops.

“You’ll hear people say after these things that they thought they were fireworks,” he said. “Well you know, that’s just not normal most places. It’s probably not fireworks. Maybe you should react to that.”

In nearly every one of the five or so talks he’s delivered, Casey said, some memory has inevitably choked him up. In one presentation with the footage from his own body camera, he had to wipe away tears when he saw his interaction with a nurse who kindly but firmly forced him to take off his bloody bandage so that she could pinch his wound together to staunch the bleeding.

“I still don’t know who she is,” he said in an interview, his voice shaking again. And he urges officers to confront the fact that sooner or later, they will likely have to respond to a mass shooting. “When I teach, I try to ingrain that this is going to happen. We’ve all been around like gunshots and shootings or whatever, but it’s usually like no more than 15 or 20 rounds. You need to know what this will sound like.”