They went to Las Vegas for what was supposed to be a fun, three-day country music concert.

On Monday morning, they returned to Denver International Airport with tearful greetings for family and friends.

Thaddeus and Kilee Oliverius, from Nebraska, told 9NEWS they were toward the back of the large crowd listening to Jason Aldean perform near the Mandalay Bay Casino on Sunday night.

It was about 10 p.m., and Aldean was in his third or fourth song, Kilee said.

At first, the crowd was confused, mistaking the automatic gunfire for fireworks, Thaddeus told 9NEWS.

Kilee said her husband was still singing along to the song before a second burst of shots snapped everyone away from the music.

Kilee Oliverius told 9NEWS he was at the concert in Las Vegas Sunday night when a gunman opened fire from a nearby hotel room. 

"We thought it was fireworks, and then after the second round we realized it was gunfire and we all hit the deck," Thaddeus said at DIA Monday. "After that, the bullets started flying everywhere."

Kilee said her brother, who was up front near the stage, crawled underneath it to escape.

Thaddeus Oliverius told 9NEWS he was at the concert in Las Vegas Sunday night when a gunman opened fire from a nearby hotel room. 

"It was like you were in a war zone," Thaddeus said. "People running and dropping, screaming and yelling."

The couple says they could hear bullets whizzing by their heads as they huddled under some bleachers. At a break in the gunfire, they took off, crawling out of the area.

"Bulldozed through fences, pretty much," Thaddeus said.

Shannon Beck, a mother of two boys from Lakewood, Colorado, was also at the concert.

LISTEN: Colorado woman describes terror, horror during Las Vegas concert shooting
Editor's Note: Some of Shannon Beck's description may be difficult to listen to. It describes what she saw as shooting broke out Sunday night.

She too had gone to Las Vegas for a relaxing weekend, celebrating some time off from the two jobs she works. It was supposed to be a girls' weekend, stress-free.

They snapped pictures before the show, anxious to hear Jason Aldean perform.

Then, they too heard, "pop pop pop pop pop." Beck said they continued singing, believing the pops were fireworks going off in the crowd in front of them.

Shannon Beck (L), with her friends before shooting broke out on the Las Vegas Strip during a Jason Aldean performance.

After the second round, people started to drop to the ground.

"There was nowhere to go," she told 9NEWS over the phone on Monday. "I started seeing people in front of us start dropping."

"We started seeing people run up past us with blood, holding their arms and their faces, yelling and screaming that they’re shooting," Beck said.

Everyone dropped to the ground, at first unsure if the shots were coming from inside the crowd, she said.

She and her friends survived by diving behind the bar in the middle of the venue, then they continued to run all the way to the end of the strip.

"It sounded like the shooting kept getting closer and closer, so we jumped a fence and tried to scramble behind some bleachers to hide," Beck said. "We kept seeing people run at us with just blood everywhere."

People and police officers were hiding everywhere: on the strip, in bushes, under cars, and behind port-a-potties, she said.

At one point, Beck took out her phone to try to record a message to her friends in case she "couldn't find a way out."

She abandoned the recording when more gunfire broke out and her group continued running.

"Everyone around us just kept dropping," Beck said. "I just wanted to get a message out to let everyone know we were safe so far."

What she described is hard to imagine. It was sheer horror.

"There was so much blood," Beck said. "Everywhere. On everybody. Some of it was splattered, some of it was people holding their necks... and people holding their fingers in strangers' wounds."

She made it safely back to her hotel and said she hopes to fly home Monday evening.

"It was supposed to be a fun girls' trip," she said.

If you'd like to help victims of the Las Vegas shooting, read this story.