Bob McAllister narrowly escaped death himself by collapsing to the ground and 'playing dead' after a bullet grazed his forehead.
Bob and his friend Hector McMillan were missionaries working in Congo during the chaos that followed the country's independence from Belgium in 1960.
In July 1964, Bob, Hector, their wives and children and other missionaries were taken hostage and held for four months in the city of Stanleyville (now known as Kisangi).
On 24 November 1964, the defeated rebel leadership ordered its troops to flee and kill as many white people as they could.
"Hector and I were taken outside," says Bob.
"As we were walking out, they suddenly opened fire on Hector and he was killed by four bullets in the back.
"Then they turned their guns on me and opened fire in all directions.
"One bullet grazed me on the forehead and I threw myself down and played dead and they passed me by.
"Hector's children witnessed his murder."
Bob, his family and the rest of the hostages were eventually rescued, but they had to leave Hector's body behind.
Bob's daughter Ruth remembers the terrifying journey to freedom.
"I remember being in the jeep and a Cuban man had me perched on one knee and a machine gun on the other," she says.
"He was shooting all over the road and I remember feeling the hot shells falling on my body."
"They sped us to the airport as fast as possible," adds Bob. "The plane was laden with stretchers. It was just taking off when a rebel shot at us puncturing a fuel tank and the pilot just about got us to safety."
The McAllisters spent three decades living and working in Congo. Hector McMillan was not the only friend the family lost during that time.
His late wife Alma's best friend Ruby Gray from Dromara was murdered along with five other missionaries, close to the town of Banalia.
Says Bob's youngest son David: "The killing of the six missionaries was very savage.
"They weren't carried out by gun, these were machete and spear killings. None of us can understand why.
"Some of the missionaries' bodies were thrown in the river and eaten by crocodiles.
"Local people say that when they threw Ruby into the river after she had been speared, she wasn't dead. And as she was sinking, she raised her hands and her last words were 'Glory to God'".
In 2014, Bob, now 90, returned to Congo with his eldest son Billy and daughter Ruth to visit Hector's grave and attend a memorial service in Banalia to honour the six missionaries, including Ruby, who were murdered by Simba rebels.
The Simbas had emerged out of the chaos that followed Congo's independence.
The movement's leaders aspired to a communist state, but most of their followers were illiterate tribesmen steeped in black magic and witchcraft who were simply looking for the better life they had been promised after independence.
The McAllister's trip is documented in BBC One Northern Ireland programme, A Deadly Mission: Belfast to Congo, which will be broadcast at 21:00 BST.
As well as paying his respects to Hector and attending the memorial service Bob also witnessed the progress made by some of the churches he and the other missionaries helped to set up in the 1960s and 1970s.
He says: "When we were being held hostage, a rebel told Alma and me 'There is no God. There are no Sundays anymore. We are going to wipe out the church of Jesus Christ'.
"But in that same area, there are more churches today than there ever were before.
"It's been worth everything we went through."
A Deadly Mission: Belfast to Congo, BBC One Northern Ireland, Thursday 30 July, 21:00 BST.
A Belfast man has recalled how his best friend was shot dead in front of him by a firing squad of Congolese rebels in 1964.