When a bomb exploded in his home during the Vietnam War, Ho Van Thanh grabbed his then-infant son and ran into the jungle.
This week - 40 years later - the pair reportedly emerged. They say they survived by cultivating forest vegetables and hunting animals, and wore loin cloths made from tree bark.
Ho Van Thanh, 82, and his 41-year-old son Ho Van Lang were found living in a forest in central Vietnam after they went missing during the country's war with the United States.
A screen shot from Vietnamese television shows Ho Van Lang, who reportedly spent 40 of his 41 years living wild in the jungle.
The older man could communicate a little in the Cor ethnic minority language, but his son only knew a few words, an official at Tay Tra commune in Quang Ngai province said on Thursday on condition of anonymity.
Thanh was last seen running into the woods with his son after a bomb exploded in his home, killing his wife and two other children in 1973, newspaper Dan Tri reported.
They were discovered when two people from a nearby village ventured 40 kilometres into the forest looking for firewood and spotted the two men's treehouse. The villagers reported the find to local authorities who recovered the pair on Wednesday.
The father and son's residence, as shown on Vietnamese television.
The two men had no contact with the outside world, the report said. Photographs in local media showed the younger man with dishevelled hair wearing a loin cloth made from tree bark.
Thanh, who was fighting for North Vietnam when the bomb exploded, left behind another son, Ho Van Tri.
"My father is very weak and the doctors are taking care of him, but my brother's health is fine even though he looks very thin," said Tri, who was six months old when his father fled into the jungle.
Thanh is being treated at a medical centre while his son is being looked after by his nephew, Ho Ven Bien.
"My uncle doesn't understand much of what is said to him, and he doesn't want to eat or even drink water," Bien said.
"He's very sad. He doesn't say anything now," he said. "We know he wants to escape my house to go back to the forest so we have to keep an eye on him now."
Hoang Anh Ngoc, chairman of the district, said local authorities had visited Thanh at the medical centre and given him food.
"I asked officials to keep a close eye on the two men to make sure they don't escape back into the forest," he said.
The discovery has shaken the small community, which thought the two men dead.
"No one could imagine Thanh and his son could live 40 years in isolation in the hard conditions of the jungle," said villager Ho Van Xanh.
There are more than 33,800 Cor members living in Vietnam, mostly in a few districts in Quang Ngai and neighbouring Quang Nam province.
Of the 18,500 people living in Tay Tra district, 95 per cent belong to the Cor ethnic group, district chairman Ngoc said.
They make a living mostly from farming cassava, grains and cinnamon.
In the past, all family names were given as "Dinh" but since the war it has been replaced with "Ho" in honour of North Vietnam's first president and revolutionary hero Ho Chi Minh.