A terrible shooting at the Mandalay Bay Resort and Casino in Las Vegas Sunday night left 20 people dead and over 100 more injured.

In the wake of the shooting, the Las Vegas Police Department said that “one suspect is down” and they did not believe there were any more shooters.

The final night of the Route 91 Harvest Music Festival was taking place across the street from Mandalay Bay when the shooting took place and concertgoers were caught off-guard.

“We were just at the concert there, and Jason Aldean was playing,” one of the concertgoers, named Mike Cronk, 48, a retired teacher, told ABC News. “Kinda sounded like some fireworks going off. I think there was the first kinda volley, and then all of the sudden second volley. My buddy’s like ‘I just got hit, ya know.’ He got hit three times. Then people started diving for the ground. And it just continued.”

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“It was pretty much chaotic,” Cronk continued. “Lots of people got hit. …It took a while to get him out. We had to get him over the fence and hiding under the stage for a while, ya know, to be safe. And finally we had to move him because he had three chest wounds.”

As bursts of gunfire crackled in the air, people outside of the casino ducked and screamed, according to video filmed by witnesses.

“We’re going to get trampled if we don’t go,” a bystander could be heard saying in a dramatic video of the incident. Confusion appeared to abound as those outside fled the scene with another person saying, “it’s fireworks.”

Another witness, Jake Freeman, said he was standing on the rooftop of a nearby hotel when the shooting broke out.

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“I had a bird’s-eye view” of the shooting, Freeman said in a phone interview with ABC News. He said he saw “crowds of people running” as people “dropped to the ground.”

“At the moment we didn’t realize that they were being shot,” he said.

The Las Vegas Police Department said people should avoid the area. Flights in and out of the McCarran International Airport in Las Vegas were temporarily halted due to the incident.