A flash flood barreled through a popular Arizona swimming hole where more than a hundred people were taking refuge from summer heat, killing at least seven people, leaving many more missing and forcing survivors to cling to trees in the rocky terrain, officials and a witness said.

Meteorologists had issued a flash-flood warning surrounding a popular swimming area inside the Tonto National Forest before the wave of water gushed through the narrow canyon on Saturday afternoon.

A woman who was hiking to the swimming hole said she saw people clinging to trees after the water rushed down a normally calm creek near the trail.

Video that Disa Alexander shot shortly after the flood showed a man in a tree holding his baby as water rushed around him. His wife was a short ways away from him, also clinging to a tree.

There was no warning before the wall of water hit, Alexander said.

The deaths include at least one child. Four people rescued by helicopter Saturday were taken to the hospital for hypothermia.

“It’s pretty much recovery (now). We don’t believe there’s anybody left out there,” Water Wheel Fire and Medical District Fire Chief Ron Sattelmaier said

The weather service estimates that up to 1.5 inch of rain fell over the area over an hour, and that the drainage took at least 30 minutes to reach the swimming hole. The thunderstorm hit about 8 miles upstream along Ellison Creek, which quickly flooded the narrow canyon where the swimmers were enjoying a cool dip a on a hot summer day, with highs in the 80s.

“They had no warning. They heard a roar, and it was on top of them,” Sattelmaier said.

There had been thunderstorms throughout the area near Payson, about an hour and half’s drive from Phoenix, but it wasn’t raining where the swimmers were at the time. But it happened during monsoon season, when whether like this can strike furiously. Monsoon thunderstorms are a common, nearly daily occurrence in Arizona thanks to the mix of heat and moisture in the summer months.

“I wish there was a way from keeping people from getting in there during monsoon season. It happens every year. We’ve just been lucky something like this hasn’t been this tragic,” Sattelmaier said.

The flooding came after a severe thunderstorm pounded down on a nearby remote area that had been burned by a recent wildfire, Sattelmaier said.

The prospect of brewing monsoon thunderstorms and the deep burn scar over the ground that had charred away the pine trees, foliage and ground dust that would normally absorb rain were such a concern that the National Weather Service issued a flash-flood warning about an hour and a half before emergency crews were called to the scene.

“If it’s an intense burn, it creates a glaze on the surface that just repels water,” said Darren McCollum, a meteorologist. “We had some concerns. We got a lot worse news.”

[Featured Image: YouTube/screenshot]