"I walked to the front of the lounges and all I could describe it as was a war zone," John Kline said. "There were people covered in blood."
He said he saw a man shot in the neck and women with a grapefruit-size stomach wound.
"It was an exit wound. She had been shot in the back as she ran," Kline said. "I had no firearm with me, It is one thing to deal with it as a police officer but it is very different with your wife at a concert."
It all began with a few pops.
"We thought we heard what sounded like fireworks...we were leaving because it was the last song and I presume people were getting a little rowdy," Kline said.
"I've been shooting and around shootings in my 15 years and to me it sounded too echo-ey to be gunshots and I assumed it was firecrackers."
It turned out it was gunfire coming from the 32nd floor of the Mandalay Bay Resort and Casino tower nearby. A gunman opened fire on the concert, killing nearly 60 people in the worst mass shooting in modern American history.
The crowd panicked and as Kline and his wife approached the VIP lounges, "we actually heard shots whiz past and strike either a metal banister or the VIP trailers," Kline said. "This was real…. I told my wife to get down low…. There were only two exits and running wasn't going to work. The shooting after an initial tap tap tap turned to automatic gunfire," he said.
A security guard was screaming at people to leave the venue, Kline said. Knowing they could be running into a second shooter, instead they hid by the VIP lounges. He said he told his wife to hide under the apron if an attacker came as he went back out front to assess the situation. That is when he took a look outside and saw carnage like he had never seen before.
Kline said he told his wife not to panic and not to look where many people had been shot and some were dead. They then walked a few blocks and called their children to let them know they were safe.
"In my 15 years I've seen some stuff and done some stuff but it's a whole different ballgame when it's your family involved," he said.
Joel Twycross was another off-duty law enforcement officer listening to Jason Aldean close out the three-day country music festival. Twycross has worked for the LAPD for nine years, and is now an officer in the department's West Traffic division.
He and a friend were grabbing drinks toward the back of the venue when he heard the first pop. Twycross initially thought it was an issue with the speaker, he said.
Then he heard it again. "That sounds like gunshots," he thought.
Suddenly, people began running and screaming. Bullets sprayed a table in front of Twycross and his friend. They hit the ground, then took off running.
As Twycross ran out of the venue, he said, he saw people pointing toward the glimmering Mandalay Bay. He could see a muzzle flash at one of the windows.
"We train to respond to these active shooters — not to be involved in one at a random place," he said. "You don't show up to Vegas for a country music festival thinking this will happen."
The officer described a frantic scene: people hiding behind metal bleachers, Las Vegas police officers shielding people with their own bodies. Twycross tried to help keep people calm and moving quickly, he said. At one point, he said, he grabbed a girl frozen in panic and told her to run.
"Let's go," he told her. "We need to move."
The officer saw people around them hit the ground.
"You couldn't tell if they were dropping because they were shot or dropping because they were ducking," he said.
Twycross ultimately made it to the Tropicana, and then the MGM Grand -- far enough away from the shooter that he felt safe.
Twycross described the experience as being "stuck in the middle" of a flight-or-fight response. He reverted back to his training, he said: You hear gunfire, you get down and you stay covered. But he was also without a weapon, as none were allowed inside.
Twycross said his captain had already asked him to talk about the shooting with other LAPD officers at roll-call meetings. His advice?
"Be mindful. Be ready. Be prepared," he said. "Don't ever think it can't happen to you."