Renee Cesario was watching country singer Jason Aldean perform at the Route 91 Harvest festival when she heard loud noises that “sounded like fireworks”.
Unbeknown to her at the time, the sounds were actually coming from the 32nd floor of the nearby Mandalay Bay hotel, where a 64-year-old man was opening fire on the crowd.
The attack left 59 people dead and 527 injured.
Days later, Renee has shared that it if wasn’t for the actions of a man she had met just two hours before the attack began, she may have been among the victims.
Her story was shared on the Love What Matters Facebook page, with Renee saying she met off-duty US Marine Brendan Kelly just two hours before the show.
"I left my friends so we could go up super close to the front for the end of the night. We were just dancing and having fun and then all of the sudden there were loud noises that sounded like fireworks, but no lights were going off," she said.
"It stopped, and Jason Aldean kept playing but then the shots fired again and he ran off the stage."
Before she had time to digest what was happening, Brendan had tackled her to the ground.
"[He] covered me from the fire," she said.
"He looked around to see what was happening and then [the shots] just kept going. He looked at me and said 'We have to get out of here. We can't stay here. It's not safe'.
"Then he pulled my arm up to get me out of the piles of people. We had no idea who was dead or who was alive. We just started to run.
"He kept telling me it was going to be okay and to keep running until we were safe...The whole night he didn't leave my side."
Brendan even let Renee use his phone to contact he sister, Jenn, who shared the texts on Twitter.
— Jenn_aayyyy (@JennCesario) October 2, 2017
"I am so extremely grateful to Brendan and his selfless act!! If he wasn't there that night, we could have had a totally different day..." Renee's sister Jenn wrote on the Facebook post, which has been shared almost 135,000 times.
"My sister is my best friend in the entire world and God knew losing her would not be ok with me."
Others praised Brendan for his act of bravery.
"You are without doubt a shining example of what people need in today's world, a real life role model, just a great young man doing the right thing for no reason other than because you were needed and put others before yourself!"
LISTEN: Mia Freedman and Amelia Lester discuss the deadliest mass shooting in modern U.S. history on Tell Me It's Going To Be Okay.
Others were more interested in where the pair's relationship would go from here.
"It takes one stranger to change our lives forever...I think you just found your soulmate," one person wrote.
"Okay seriously, MARRY HIM. Don't let him go," said another.