Phoenix fire officials say the 14-year-old and his family ran out of water during their more than four-hour hike in triple-digit heat Sunday.
Fire Capt. Alex Rangel said the teen started acting confused, walked off a trail and then lost consciousness.
By the time firefighters reached him a half hour later, the teen was not breathing and he didn't have a pulse.
Maricopa Medical Center spokesman Michael Murphy said Monday that the teen was pronounced dead late Sunday afternoon.
The teen's family members were treated for dehydration.
Temperatures in the preserve ranged from 105 to 110 degrees late Sunday morning.
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