The bullet left a wound in his upper left chest about 7mm wide, and was still embedded as he was flown to Auckland City Hospital.
He was "confused", barely talking and semi-conscious in a "nearly dead" state, Mr Driessen said.
Officers were still at the property yesterday completing a scene examination. They had spoken to the slaughterman and were also interviewing witnesses.
The closest home-kill service to Peak Rd is Kaipara Meat Processors. When contacted yesterday the manager hung up on the Herald after saying: "No thanks, no comment."
The Department of Labour confirmed it had also launched an investigation into the shooting, but could not comment further last night.
A West Auckland slaughter assistant said last night that bullets ricocheting off beasts were common.
"It is quite easily done," she said. "If it's an older animal they have really heavy heads and a bullet can ricochet off very easy. But it's a real fluke that it happened and it hit someone."