The horror in Orlando is sadly familiar to Dr. Chris Colwell, an emergency medicine manager at Denver Health.
He was one of the first on the scene at Columbine and worked overnight treating patients wounded in the Aurora theater shooting.
"There's no way you can completely and adequately prepare for an event like this. You can't, so you feel inadequate," said Dr. Colwell.
Colwell has been on the phone, offering support to the emergency responders in Florida.
"The providers at the scene, the providers at the emergency department, the providers at the operating room, remember those folks, follow up with them, and be sure they are having their needs met," said Colwell.
He knows they, too, may need mental health treatment, along with the people inside the nightclub. He wants to remind them not to ignore their own emotions in the days, weeks and months after the shooting.
"The response is dramatic and it is very real. And if we don't recognize it, we can't always prevent things from happening, and providers from really struggling from this, but we can certainly help them get through that process."
In the years following the Columbine and Aurora shootings, Colwell has spoken to this colleagues in other cities. He is sharing his personal and professional experiences with the goal of helping others handle the unthinkable.