"It was on its stomach with its back legs dragging, with its head in the air."
He said the dog had a lead tied to its neck, which was attached to the towbar of the silver SUV. He estimated the vehicle was travelling about 60km.
The driver was leaving the highway and turning into unsealed Ambler Rd, when Roos was driving past.
"It looked like a light brown pit bull. I stopped as fast as I could and turned to confront him, but I believe he saw me stopping and he drove away fast."
After giving chase, Roos said he believed the driver turned into one of the first driveways along Ambler Rd.
"I did drive at quite some pace to the end of the road and at that point the gate was closed and no dust in the air."
Roos said he considered walking on to the private properties to find the driver but decided it was a job best left to the police.
"I didn't go in, because if you could do that to a dog imagine what they would do to a person," he said.
When driving back on the highway, Roos said he looked at the surface and saw what he thought was blood on the road.
"I am not sure how far the dog was being dragged before I saw it.
"I have played the image through in my head quite a few times and I can say for sure that it did look [dead] at that time.
"I also thought it could be a dead dog but I cannot think why anyone would drag a dead dog home if it was a pet. It makes no sense to me."
He said he drove to the nearest police station in Rawene to report what he saw and also left a voicemail message with police.
A police spokeswoman confirmed police received the phone message and were today making further inquiries.
Roos said he had also alerted the SPCA.
Bay of Islands SPCA centre manager John Logie said an inspector was investigating.
"We're doing everything we possibly can to find the dog and the person responsible for this.
"We're urging anyone who witnessed this, or has any more information about the case please call us urgently on (09) 407 7515. Any information will be kept strictly confidential."
