Bruce Scott was convicted and sentenced in the Waitakere District Court for careless use of a firearm.
The charge related to an incident on a farm in Helensville, West Auckland, in March. Scott accidentally shot his assistant, Simon Alex, 18, after a bullet ricocheted after hitting the head of a cow he was trying to kill.
The bullet ripped through Alex's upper body, puncturing his left lung.
Alex nearly died twice during the ordeal but recovered after Scott performed CPR with Westpac Rescue Helicopter assistance.
Scott told the Herald on Sunday he was about 45m from two wild and dangerous 5-year-old cattle when he fired his rifle.
"Alex was about [24m] from the cattle, up a gentle slope," Scott said. "He was instructed to go behind the shed. Simon chose to come forward and watch.
"The bullet passed through the beast's skull then deviated its flight path into Simon. If he had been where he was instructed to be, he never would have been injured."
Scott pleaded guilty but requested a discharge without conviction so he could fulfil his dream of trying to qualify to compete in shooting at the Rio de Janeiro Olympics in 2016.
He said he had never had an accident in the 15 years he had slaughtered animals.
"This was a freak accident that could not be replicated, even if someone tried to. How could I have prevented such a freak accident?"
Alex initially supported his bid to avoid a conviction in an affidavit but later changed his statement when their relationship ended, he said.
"He went to work for the opposition and it all turned sour," Scott said.
"He has now made himself look real stupid in the community." Scott offered to pay Alex $3000 compensation, which the judge accepted.
