It seemed like a dream vacation for William Cybulski as he sat in Disney World on Sunday night.

The Buffalo firefighter was relaxing by the pool – watching a Buffalo Sabres game – with his girlfriend and her two young children at one of Disney’s theme resorts.

But when Cybulski’s girlfriend went to check on the kids, they both realized that tragedy had struck.

“I could just hear my girlfriend scream from the pool, and when she screamed like that, I knew something was wrong,” Cybulski said.

A boy from another family was lying unconscious in the 4-foot-deep water. Disney’s lifeguards had apparently just left the pool for the night.

“It was the off-season, so it’s like a swim-at-your-own-risk kind of thing,” he said.

The South Buffalo resident jumped into action, rushing to the boy’s side as a nearby doctor tried to resuscitate the 13-year-old.

Cybulski, 27, dried the boy off and helped the doctor. Another nearby firefighter rushed to the scene.

Meanwhile, Cybulski’s girlfriend comforted the boy’s brother and ushered the few dozen children out of the pool.

“You see somebody in an emergency, and you just want to help, to do all you can,” he said.

But their efforts were for naught. The boy never regained consciousness at the scene. He died Tuesday morning.

“It’s sad to see that he didn’t survive,” Cybulski said. “If they would have pulled him out a couple minutes earlier, you never know.”

The whole thing happened so quickly, Cybulski said, and was surprising given the relative shallowness – 4 feet, 6 inches – of the pool.

“A 13-year-old boy, you’re not really going to think much of it in a small pool with 30 or 40 kids in the pool,” he said.

Especially not in a place that bills itself as the “happiest place on earth,” he said.

“You never want to see a child pass away, but especially on vacation at Disney World,” he said.

“The last thing you expect is to be on vacation and something like that happens.”

He added that his family’s concerns were small compared with the suffering of the boy’s family.

“Our prayers are with them,” he said.

“We have a lot of people praying for them, and hopefully they can get through this. Hopefully they can overcome the tragedy.”