Christopher Hansen said he was getting a drink at the bar when he heard gunshots inside the Pulse nightclub in Orlando during the early hours of June 12.
"You could still hear the gunshots," Hansen told ABC News. "It was like the length of a song. It just kept going, 'Pow, pow, pow, pow. Just non-stop, continuous, and then just sort of brief silence and then it went all over again. So, I don't know how many rounds were shot. It was just like, shot, after shot, after shot."
He added: "Once I saw the bodies dropping, the people screaming...you could see the blood everywhere. The person next to me was shot and I dropped down so that I could crawl out...I wasn't [thinking]. It was like my mind was saying, 'Get out. Get out.'"
Sunday's massacre would become the worst mass shooting attack in U.S. history.
Hansen recalled crawling his way out of the building before coming to the aid of gunshot victims, including one man who was shot in the back.
Hansen said he and another club goer used a bandanna to stop the stranger's bleeding. The victim did not speak English. Hansen did not know if the man survived, he said.
"He was completely drenched," Hansen said.
Hansen said he also helped a female victim control her breathing after she had been shot.
"I was with her trying to help her to control her breathing, 'It's OK, stay calm, just breathe,'" Hansen recalled. "She was from Ohio as well...she's a tourist, I'm a tourist so we were able to talk about that and just to keep her alive. That's what we tried to do."