Beierman had taken a day off work and let his son miss school so they could go on a bear hunt near their family cabin in western Wisconsin.
When Owen came across the creature he fired at it and wounded it, prompting it to flee while the father and son duo tracked it through the woods.
It was only later in the day, after darkness had fallen, when Beierman came across the bear – just five or six feet away from him.
“He was in a stance like a cat about to pounce,’’ he said. “The next thing I know he was on me. He charged and knocked me down.’’
Recalling the bear’s hot breath as it sank its teeth into his face, he frantically thrashed about, trying in vain to break free and get out from under the enormous creature that had pinned him down.
“The bear was fighting for its life, and I was fighting for mine,’’ he said.
The pair were locked together in a desperate struggle for around a minute, with Beierman desperately hitting the bear with the blunt edge of his empty pistol to little effect.
“Before I knew it I was flat on my back. I started pistol whipping him and it felt like I was striking a brick wall. I remember thinking: “You have to do something different,’” he said.
When the bear reared back and lunged for Beierman’s face, he lifted his right arm to block the renewed attack and heard a “crunch”. The bear had only punctured the skin but at the time he believed his arm was broken.
Saving his father’s life, Owen intervened, killing it with his 350 Legend hunting rifle.
“I didn’t think twice,” Owen, a young hunting enthusiast whose family home is full of trophies from past expeditions, told NBC News. “I just shot it.”
“I was flat on my back and could feel the bullet going through the bear. Owen was a hero. He shot that bear and killed it on top of me,” Beierman said.
The 43-year-old was left bleeding profusely after the mauling, and was taken to hospital in an ambulance after his neighbours called the emergency services.
He couldn’t even manage to call his wife as too much blood was falling on to the phone screen. “Owen, still composed, helped me with all of that,” he said.
Beierman’s left cheek had been sliced open and had to be reattached with 23 stitches, while teeth marks were left in his forehead.