The defendant's son spoke to the men briefly before retiring to the lounge.
Moments later, Herzog walked up to the victim, who was sitting on the couch, placed the gun against his son's right thigh and pulled the trigger.
He then pushed it against his left upper arm and shot him again.
Herzog stated: "I shouldn't have done that", and left the room, while the victim pulled the staples out of his flesh.
When spoken to by police, he claimed "it was only a bit of fun".
The defendant subsequently pleaded guilty to injuring with reckless disregard and appeared in the Dunedin District Court yesterday.
"It was a stupid game of Russian roulette, really," Thorburn said.
She said the incident had driven a wedge between father and son, which was especially tragic, since her client had raised the victim alone.
The pair had been in contact through social media and were repairing their relationship, though, Thorburn said.
"He tells me he can't say sorry enough."
Judge Kevin Phillips noted the victim, who had a mild intellectual disability, did not want to sit down with Herzog for a restorative-justice conference.
"I didn't know he was going to do it. I feel hurt inside when he used the staple gun on me," the 21-year-old wrote in his victim impact statement.
The conviction was Herzog's first for violence but the judge highlighted an "appallingly bad" driving history.
Herzog was sentenced to nine months' supervision and 100 hours' community work.
