"All of a sudden a cop comes out from between the cars with a rifle and shot it in the head, he then walked up closer to it and shot it in the head again – in front of everyone.
"I'd literally just said to my girls 'hey, look there's a cow' and then bang - that happened. It was surreal."
Robert said he had his 3 and 4-year-old daughters in the car who saw everything.
"Afterwards my 3-year-old stuck her head in the car seat and covered her face as she was a bit scared and didn't understand."
He was shocked that they were not given any warning before the shooting.
"It was only about 25m away from where we were parked. I think there should have been a spotter or somebody behind to warn people to look away,"he said.
"I thought it was weird that someone could discharge a rifle, and twice, with no warning for anyone.
"There were a lot of families coming back from holiday that may not have ever been around firearms before, so to have one discharged within metres of their car would have been a bit shocking to them."
Robert said it was "pretty s*#t" for people to witness, but he thought it was a better outcome than the steer going through someone's windscreen.
A police spokeswoman said that just before midday on Saturday they receive a report of a cow on the shoulder of the road on SH1 at Orewa.
"Police made numerous attempts to get the cow off the road and into a paddock safely but unfortunately this not successful and the cow was shot for public safety.
"Situations like this are dynamic and fast-moving and Police are required to make decisions in a matter of seconds to ensure the public are kept safe."