Two French hikers were killed in White Sands National Monument, located right outside of Las Cruces, N.M., last week. Authorities said they succumbed to heat-related issues. (Photo by Robin Soslow)

A French couple who set out with their 9-year-old son on a deadly hike in the New Mexico desert on Tuesday may have lost their lives in an effort to keep their child alive, according to news reports.

David Steiner, 42, and Ornella Steiner, 51, both of Bourgogne, France, gave the boy two sips of water for each one they took before their supply ran dry and they succumbed to the scorching heat in the White Sands National Monument, Otero County Sheriff Benny House told the Associated Press on Friday.

“That may be why he fared so well, is he was a lot smaller and probably had twice as much water,” House said, referring to the child. “He was well hydrated, compared to the other two.”

Park rangers discovered the three French nationals while patrolling an area about 1.5 miles from the Alkali Flat trail head on a day in which the temperature reached 101 degrees, according to the AP. The child was found alongside his father and rushed to a hospital, where he spent the night and was treated for heat exposure. The boy’s mother, who was eventually located by herself 1 1/2 miles from the Alkali Flat trail head, had complained of feeling ill before she collapsed, authorities said.

“So she made the decision that you guys go ahead and go on, I’m going to go back to the vehicle,” House told the AP. “She made it about 100 yards before she went down.”

House told the AP that the father and son continued on the trail unaware that Steiner had succumbed to the heat. He said the father traveled another 2,000 feet before he also collapsed.

Authorities believe the couple died of heat-related causes, House told the AP. Officials are awaiting the results of an autopsy to confirm the official cause of death, according to the AP.

Authorities said the family made a fatal mistake by setting out on their hike with only two 20-ounce water bottles, far less than the one gallon per person recommended by White Sands park rangers, according to ABC affiliate KVIA. The trail lacks vegetation and shade, and visitors are warned to avoid hiking in the hot, midday temperatures, according to the AP.

The boy, who authorities did not identify, may not have survived if authorities had not reached his mother, leading them to take a look at her camera. Once they did, House told the New York Daily News, they realized she wasn’t alone and they needed to find her companions.

“We were trying to figure out what was going on,” House said. “We looked at the camera. Otherwise, he could have been the victim as well.”

House told the Daily News that, until this week, two people had died from exposure in the area over the last 15 years.

“It’s not common out there,” he said. “It has happened, but it’s very rare. It’s a tragedy.”

The boy’s grandmother flew to Albuquerque and was reunited with him Thursday.

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