WATCH: Jason Aldean Reflects On Route 91 Mass Shooting

Jason Aldean reflected on the mass shooting at the Route 91 Harvest Festival in Las Vegas last October during an appearance on Ellen.

In the episode that aired Monday, the country singer said he didn’t know that a gunman had opened fire on the crowd until he was off stage.

“It took me awhile to realize,” he recalled. "Nobody knew what was happening. That’s the last thing you think is going to be happening during a show so I think everybody was just kind of stunned.”

Aldean said visiting survivors in hospital a few days after the attack had a big impact on him.

“I felt like people were there to see my show and obviously the last thing you want is for anybody to get hurt,” the singer said, “so it was tough to go back to see people in the hospital and some of them in comas and things like that.”

Aldean called it “one of the hardest things I probably ever had to do.”

But, he added, “seeing them and some of the strength they had, just being happy to be alive and make it through that, it sort of allowed me to look at it in a different light. I got nothing to be whining about.”

MORE: Jason Aldean Opens Up About Vegas Tragedy

While accepting Entertainer of the Year at Sunday night’s ACM Awards, Aldean said: “It's been a rough year and I just want to say thanks to everybody that reached out to us and showed us love and support over the last six months.

“To my Route 91 people, you guys are in my heart always and we love Las Vegas. Vegas strong, baby — thank you so much.”

Watch Aldean on Ellen below: