Story highlights Crews are trying to locate Hector Miguel Garnica

Five of the dead were children, Gila County Sheriff's Office says

(CNN) A family gathered at a popular swimming area north of Phoenix to cool off from the desert heat and celebrate a birthday.

Heavy rain was falling eight miles upstream from where they played, but skies were apparently clear where they were. Even if they had heard or seen the flash-flood warning from the National Weather Service an hour and a half earlier on their smartphones, it's hard to imagine they could have anticipated the devastation about to hit them Saturday afternoon.

Summer fires had cleared ridges and slopes of vegetation, so there was nothing to slow the tremendous volume of water that swept down on them so quickly, on land baked to repel water by constant high temperatures.

"They had no warning. They heard a roar and it was on top of them," Water Wheel Fire and Medical District Fire Chief Ron Sattelmaier told the Arizona Republic

Reportedly up to 6 feet high and 40 feet wide, the waters swept away 14 members of the family, carrying them fast and far downstream.

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