"That cop's death just shows what sort of damage they can do. The modern-day air rifles are pretty dangerous, they are pretty powerful machines."
Officers said the metal surface Simpson was shooting at presented a risk of ricochet but he continued firing the pistol despite the risk.
Police were rung by a man in a neighbouring property who could hear the metal ball bearings strike against the warehouse he was working in.
Grant Galgey said he called police because he was frighteneed that one of the projectiles could injure someone.
"I was concerned that it was some young person being an idiot.
"He was shooting all over the place but it was dark and no one was around. When they started pinging off my building that's when I got a bit worried the ricochet could go anywhere.
"He was being a silly boy and I hope that he has learnt his lesson that you can't just shoot your slug gun off anywhere."
Police soon swarmed the area and reported hearing at least two pellets fired from Simpson's unit which struck the car wreck at "very high velocity".
They appealed for Simpson to go to his door and detained him. Two air rifles were also found inside the apartment.
He appeared in Napier District Court last week and pleaded guilty to one charge of discharging a firearm near dwellings. He was sentenced to 60 hours community work.
The charge carries a maximum penalty of three months' imprisonment.
In an explanation to police Simpson said he had been shooting at mice in his back yard as well as the old car wreck and acknowledged it was reckless and the pellets could have easily caused injury to other people in the area.
In January, a Napier teenager was sentenced to 100 hours' community work for accidentally shooting a 12-year-old boy with an air rifle as he left Tamatea Intermediate School grounds last December.
The teenager, then 17, had been shooting targets with friends in the backyard of a neighbouring property when a bullet went through a crack in the fence and hit the 12-year-old. The bullet entered the boy's back, coming to rest millimetres from his kidney and had to be surgically removed.
The Arms Act 1983 recognises an airgun as any air rifle, pistol or weapon that has a gas or compressed air firing mechanism; including air rifles, air pistols, BB guns, soft air pellet guns and paintball guns.
Anyone aged over 18 can own and fire most airguns without a firearms licence.
Teenagers aged 16-18 require a firearms licence to possess an air rifle, but may use one under adult supervision without a licence.
A new regulation requiring those possessing high-velocity air rifles to have a firearms licence came into effect in October 2010.
