He said his friend, James, was "a bit bummed".
"Because it is a bit of a profit that has been lost on each cow. It would be about $10,000 - $12,000," Heta-Morris said.
James Miles told 1 NEWS the cows died from a single lightning strike.
"It was an unreal feeling thinking that could of easily been myself or the boss," he said
"We were milking the last row and had a little joke about better get the wife to pick him up to take him home 'cause we might get struck by lightning.
"We had a little chuckle about that and we carried on our way, and the boss left on quad bike to go home," he told 1 News.
"About five minutes later, I got a call saying to quickly turn the power off - we have had four cows struck by lightning."
Miles took the footage as he arrived back at the location on a quad bike.
It has been viewed more than 66,000 times, with hundreds of people expressing their shock at the event.
The event is just one of many storm-related incidents today as violent weather ripped through the central North Island.
The storm which pummelled Auckland this morning also saw a woman taken to hospital after a lightning strike in Māngere, caused the airport to stop refuelling planes, flights to be cancelled and delayed, and houses to shake.
More than 800 lightning strikes have also knocked out power to some rural parts of Auckland.
