(REUTERS) — An Indiana man who forced his three young grandsons to take brutal marches through the Grand Canyon during scorching summer heat was convicted of child abuse in federal court on Wednesday, authorities said.

Officials at the U.S. District Court in Phoenix said Christopher Alan Carlson, 45, was convicted on three of six felony child abuse charges in connection with one of two tortuous hikes he took last August with the boys, then ages 8, 9 and 12 years old.

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