First responders and law enforcement hit the horrific scene that occurred in Las Vegas Sunday night, ready to tend to the wounded and those in need of help.

As the world tuned into the news of a gunman who open-fired from a hotel room above an outdoor concert, killing at least 59 and wounding 527 more, authorities combed through the chaos finding those who needed medical attention.

Gunman Stephen Paddock, 64, was found dead by officers who stormed his 32nd-floor room at the Mandalay Bay Resort and Casino, said Clark County Sheriff Joe Lombardo, who announced the death toll and said it could rise.

The shooting is the deadliest in U.S. history.

The three-day Route 91 Harvest festival started Friday, and Lombardo estimated that 22,000 people were in the crowd when the shooting began at about 10 p.m. local time.

Following the shooting, Nevada hospital workers prepared for a nightmare to come to life within their hallways. University Medical Center is the only level-one trauma center in the state of Nevada.

But what does this mean?

The Office of Statewide Heath Planning and Development (OSHPD) defines trauma centers as licensed hospitals designated by Emergency Medical Services Agency (EMSA) as having the available personnel, services, and equipment necessary for the care of trauma patient.

Trauma centers are given level numbers based on the type of resources available and number of patients treated for trauma annually, according to the American Trauma Society (ATS).

There are five levels for trauma centers, but the way they are categorized varies from state to state. Adult and pediatric centers are categorized differently. For example, a level I adult trauma center can be considered a level II pediatric center.

In California, there are only up to level four trauma centers, according to the OSHPD.

Level I trauma centers have the capacity to treat total care for every aspect of injury-- from prevention to rehabilitation. They provide 24-hour in-house coverage by general surgeons, and prompt availability of care in specialties such as orthopedic surgery, neurosurgery, anesthesiology, emergency medicine, radiology, internal medicine, plastic surgery, oral and maxillofacial, pediatric and critical care, according to the ATS.

A trauma I center specializes in teaching and research efforts to help new innovations in trauma care. In California, the research and teaching facilities in a level I center is the main difference between a level II center.

A level III center provides proper assessment and initial stabilization of a trauma patient. Level III centers have transfer agreements with level I and II centers for more complex and specialized surgeries, according to the ATS. The greatest differences between level III and IV centers are surgery capabilities.

Outside of California, there are level V trauma centers, which provide the basic medical care necessary to get a patient ready for a transfer to another facility.

There is only one level I trauma center in the Sacramento region-- the UC Davis Medical Center. It serves as both an adult and pediatric level I trauma center.

However, there are several level II trauma centers in the area including Kaiser in South Sacramento, Memorial Hospital in Modesto, Mercy San Juan in Sacramento, and Sutter Roseville.

For a full list of California trauma centers visit the OSHPD's website.