FOREST FALLS (CBSLA.com) — A hiker was killed Tuesday after a thunderstorm triggered a flash flood in the San Bernardino National Forest.

The victim was hiking with his girlfriend in the Forest Falls area, south of Big Bear Lake, when she said fast-moving water swept her boyfriend away.

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“The water, according to the female, waist-deep, and they tried to cross it, which is extremely inadvisable. And again, she was able to self-extricate, and he was not able to,” said Capt. Brett Raney of the San Bernardino County Fire Department.

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Rescue crews found for the 29-year-old man’s body in the waters about a mile away from where he disappeared.

They also found a backpack with keys, cell phones and a hydration pack often used by hikers. It’s not clear if the items belonged to the victim, whose name has not been released.

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His girlfriend was also injured.