"All of a sudden the dog looked up and immediately his body language changed.
"His tail went straight, he went stiff."
The owner was still running and yelling, she said.
"I thought, 'Hell, that dog is going to attack'."
Harvey tried to take the horses into the water, in an attempt to put the dog off, but only got about two strides in. The target was the horse she was leading, a 15-year-old male named Sol.
"It charged and it flew right at the horse's chest area ... and bit the horse there, and with that the horse pulled away from me."
She said she let Sol go, wanting to let him defend himself.
The dog chased the horse on to the reserve and was right behind him the whole time, Harvey said, trying to bite at his belly.
Meanwhile, Sol was attempting to keep the dog away, kicking and stomping at it.
The dog then managed to jump up and get hold of the horse's nose, locking on.
"So when the horse lifted its head in the air, the dog was dangling probably nearly 2m in the air," Harvey said.
She said that happened two more times during the 10-minute attack, with Sol managing to temporarily dislodge the dog and flee, before it chased him down and latched on, again and again.
The horse eventually landed a solid kick and the dog was knocked to the ground.
"The horse came running back to me, and I grabbed the halter and I bolted down the beach," Harvey said.
She said people were watching on "horrified" and they told her that the man picked up the dog, got in the car and fled.
There was a lot of blood, Harvey said, and it took the vet about an hour and a half to stitch the wounds.
The most damage was to the horse's right nostril, which was "completely torn", leaving a big flap of skin.
There were also a lot of smaller 2cm to 3cm cuts on Sol's nose, she said, where the dog had got its teeth in and then "ripped" as the horse flicked away.
The horse also suffered a bite behind its front leg. Harvey is currently injecting it with powerful doses of antibiotics, morning and night.
She said she rides on the beach all the time and often dogs yap and bark at horses, and might even try give them a nip at the heels, but generally when you turn around and face them, they back off and run away.
"What happened to me on Tuesday was a deadly attack. That dog was fit to kill that horse and it was in full attack mode," Harvey said.
"It was not a minor attack, it was out to kill that horse.
"That dog will attack again and I think we got off pretty lightly really, considering the ferocious viciousness of it."
The Western Bay of Plenty District Council's manager of compliance and monitoring, Alison Curtis, said animal services had not yet found the dog nor the owner.
She said they had been taking statements from locals, had viewed a video taken of the incident from a distance, and were appealing to the public for any information.
"There's probably an injured dog out there, if anyone is aware of that."
The names that were heard being shouted at the dog on the day — "Tivo" or "Devo" or "Tebo" — had not matched with any registrations on file, Curtis said.
