A 63-year-old man sacrificed himself to save his grandson after their jeep tumbled down a mountain in New Mexico, United States earlier this month.

ABC News reported on Wednesday (Sept 26) that Mr Gerard Greenough had been on an off-roading trip with his family, and was on a mountain when the jeep that he and his grandson, 13-year-old Austyn Kerley, were in got stuck on a rock.

Mr Greenough attempted to accelerate in order to free the car, but this caused the rocks beneath the vehicle to slide, sending the jeep tumbling down the side of the mountain.

Austyn's mother Amanda Kerley told ABC News that the jeep fell roughly 150 feet (45.7m) down the mountain.

"As the Jeep tipped, my dad grabbed my son and cocooned him, to protect him from the fall with him in his arms," she said.

Austyn's father and brother managed to reach him and pull him back up the mountain. Two passers-by rushed him down the mountain trail to an ambulance, and Austyn was later airlifted to hospital by a helicopter.

He suffered multiple injuries including major blood loss, a lacerated pancreas and liver, broken clavicles and spinal fractures in his neck and back. At one point, he even went into respiratory failure.

In spite of all this Austyn survived, was given an early discharge from hospital and is recovering at home.

Mr Greenough, however, was not so fortunate.

An off-duty paramedic who happened to be nearby went down the side of the mountain to try and rescue him, and performed cardiopulmonary resuscitation on him for around 20 minutes. Despite this, Mr Greenough did not survive.

As soon as Austyn is able, he and his family intend to hike back up to the site of the accident to honour Mr Greenough's memory.