More than 515 others were injured in the shooting, which sent concertgoers scrambling for their lives. Officials said the gunman killed himself.
"Kinda sounded like some fireworks going off," Mike Cronk, 48, told ABC News. "I think there was the first kinda volley, and then all of the sudden second volley. My buddy's like, 'I just got hit.'"
Country artist Chris Young, who also performed at the festival, tweeted, "I'm lucky to be alive."
Young, Jake Owen, Aldean, Lee Brice, Dylan Scott, Luke Combs and Josh Abbott were among those who performed at the festival.
Young tweeted, "Spent I don't know how long on the floor of a trailer behind the stage ... know multiple people are dead. Listening to that gunfire ... I'm literally shaking still."
He added, "I'm lucky to be alive. As are many others ... and so many people are gone ... this is heartbreaking."
Owen wrote on Twitter, "Gun shots were ringing off of the stage rigging and road cases. No one knew where to."
"Praying for everyone here in Vegas," he went on. "I witnessed the most unimaginable event tonight. We are okay. Others aren't. Please pray."
Owens also thanked the police and first responders "for keeping us safe."
Abbott gave an update Monday afternoon about his band, saying: "Everyone in our band and crew are safe."
"I (Josh) had just left and was in the Mandalay Bay on the 20th floor with my fiancée during the shooting just a few floors away," the statement continued. "The band & crew were on the concert grounds and saw people get shot. Some of my crew members were hit with shrapnel, but not injured. We are deeply disturbed by this horrific act of violence and send our thoughts and prayers to the victims and their families. It was a long awful night but we are blessed to be alive and healthy. Hug your loved ones tight."