An unsettling video has surfaced on social media, showing a Brazilian rancher swigging a bottle of beer while his 11-year-old son is piloting his private plane.

Mr Garon Maia, 42, and his son, Francisco, died when the same aircraft – a US$1.2 million (S$1.6 million) twin-engine Beechcraft Baron 58 – crashed on July 29 in a forest between the states of Rondonia and Mato Grosso, in Brazil.

Overcome with grief, Mr Maia’s wife, Ms Ana Pridonik, took her own life with a gun hours after her husband and stepson were buried on Aug 1.

Investigators are now trying to determine how much the father’s actions recorded in the video contributed to the tragedy.

It’s unclear when Mr Maia took the video, but investigators said what was seen in it reflected how much he regarded his and his son’s safety.

In the video, Francisco could be seen in control of the plane as it took off on a dirt runway, with Mr Maia, on the co-pilot’s seat, giving him instructions.

“Wait, everything ready? Nothing in front, okay. Come on, 600 horses, you can push. 600, Kiko, go,” Mr Maia could be heard telling his son.

“Hand on the lever, hand on the lever. Keep your hand there and look at the speed,” he said, as the plane took to the sky.

Moments later, as the plane began cruising, Mr Maia was seen downing a bottle of beer.

“The passenger can have one. Right, Kiko?” he said.

Crash investigators said on July 29, Mr Maia flew out of his ranch in Nova Conquista and then stopped at an airport in Vilhena to refuel.

He was planning to fly Francisco back to Campo Grande, Mato Grosso do Sul, where the boy lives with his mother and attends school, reported Daily Mail.

The plane took off at 5.50pm and plummeted eight minutes later.

“The plane crashed very close to the ploughed land. He didn’t have time to land,” news reports quoted one witness as saying.

Investigators are trying to determine whether his son was the one flying the plane when it crashed.