Hospitals across the Las Vegas area called for backup area after being inundated Sunday evening after mass shooting at a country music festival on the Strip, according to an article on the NPR website.
In Las Vegas on Sunday, calls were likely going out to surgeons first, but not just surgeons. "Surgeons don't work in a vacuum," Bruno Petinaux, the chief medical officer and co-chair of emergency management at the George Washington University Hospital in Washington, D.C., said.
"We're now talking anesthesiologists, we're talking about nurses, we're talking about even pharmacists coming in. You may need to bring in more cleaners to help clean the OR and turn it around quickly."
Hundreds of extra doctors in Las Vegas were called in to work Sunday night, along with another 100 people including nurses, technicians and support and environmental services staff.
Designing for Distraction: Benefits for Children, Families
Staffing and Consolidation Reshape Outpatient Facility Strategies
Adams Health Network Falls Victim to Phishing Attack
Ventilation and Filtering for Infection Control 
ChristianaCare Opens Aston Campus Neighborhood Hospital