Police were called by the ambulance service, which rushed Mr Townsley to Middlemore Hospital, but he died soon after arrival.
"They wouldn't say what happened but [another person] told me. They would only say there was a bang and he dropped to the ground."
At the time, Detective Inspector Dave Lynch said the death served as a "painful reminder" airguns were not toys and needed to be used "in a controlled environment by responsible people with appropriate target awareness and knowledge of their power".