After escaping Hurricane Harvey in Houston, Royce Christensen worked at the Las Vegas music festival.

Jill Roberts heard the screaming and crying in the Sunrise Hospital and Medical Center emergency room Sunday night as the families and friends of those killed in the Route 91 Harvest music festival shooting found out their loved ones didn’t survive the attack.

When she was under fire, dodging bullets at the Route 91 Harvest festival on Sunday, Megan Greene felt an odd sense of purpose. "If you're still breathing, you're fine," she told a panicky woman trying to escape with her mother, who uses a wheelchair.

Christie White, 46, smiles thinking of her last peaceful memory. It was a girls’ weekend. It was Sunday night. Christie and Dani and Beth were hanging out in the perfect late-summer weather under glimmering Las Vegas lights with some cocktails, and their favorite country bands.

The volunteer psychologists and counselors have been pouring into this grieving city, so fast that a state official says the supply far exceeds the demand for crisis counseling.

We often think of first responders mainly as police, fire and emergency-medical professionals. In Las Vegas on Monday, NPR's Eric Westervelt found a small volunteer army of mental-health professionals, trauma counselors, psychiatrists and social workers who quickly fanned out to help some of the thousands who had witnessed the massacre up close.