The youngsters took turns firing at the target, the police summary of facts says.
At one point, one of the boys ran through the firing line and was shot in the upper left leg by Phelps.
The other child then ran through the firing line several times as Zuppicich fired at the target. He was hit at least four times by pellets.
The next day at school, teachers noticed small bruises on the boys' legs, which they said had come after being shot by a BB gun.
Later on November 30, the boys were examined by a paediatrician at Christchurch Hospital and were found to have minor bruising.
When spoken to by police, both Phelps and Zuppicich admitted their "stupidity".
Phelps and Zuppicich both pleaded guilty to a charge of careless use of an air gun today.
They declined the offer to go through the restorative justice programme.
Phelps' defence counsel Michelle Barrell noted: "He [Phelps] is in a relationship with the mother. I believe he has probably had his own form of restorative justice within the home."
Judge Sharon McAuslan, and lawyers for both men, noted it was "very fortunate" that the incident did not result in more serious consequences.
She convicted both men and ordered that they each pay $250 to each child as emotional harm reparation.
