A flash flood swept through central Arizona on Saturday, killing at least nine people who had gathered at a popular swimming hole for a birthday celebration.
The family was relaxing alongside a mountain stream in Tonto National Forest, unaware that summer thunderstorms had just dropped heavy rains upstream.
Floodwaters six feet high suddenly swept through the canyon, according to the AP. Video shows fast-moving waters rushing through a canyon as people cling to trees. First responders called it a "40-foot-wide black wave" moving at 45 miles per hour, The Arizona Republic reports.
"We had a strong thunderstorm with strong rains move through the area, which created a flash flood problem," said Sgt. David Hornung of the Gila County Sheriff's Office. "There was a large group of people recreating along the Verde River area, and the flash flood came upon them and washed 14 of them downstream."
Search and rescue teams, including a helicopter and 40 people on foot, looked for victims. Bodies were found as far as two miles downstream, the AP reports, in piles of debris or alongside the river.
The dead were all from one family from Phoenix, the Republic reports. Authorities recovered the bodies of nine people, ranging in age from a sixty-year-old woman to her two-year-old granddaughter; one person is still missing. Four other family members were rescued and taken to the hospital and treated for hypothermia.
"They had no warning," said Water Wheel Fire and Medical District Fire Chief Ron Sattelmaier, the AP reports. "They heard a roar and it was on top of them."
The Republic reports the thunderstorm hit eight miles upstream; it wasn't even raining where the family had gathered.
The National Weather Service issued a flash flood warning about 90 minutes before the water swept through the canyon, but authorities say there's no cell service where the swimmers were, so they likely didn't know about it. The weather service says about 1.5 inches of rain fell in an hour, according to the AP.
Flash floods have killed dozens of people in Arizona in recent decades, according to the Republic. A flood over Labor Day 1970 killed 23 people near the state's Mogollon Rim.
And the threat from powerful rains continues. The National Weather Service issued a flash flood watch and warned of hazardous weather for the area on Monday morning.