While Campbell took the lead role in the killings, Mendoza became "fuelled by emotion and blood-lust''.
Mr Hargreaves told APNZ that the news of the decision brought a smile to his face.
He said the dogs were his family.
"You go home to your wife and kids... well, that's what it was like for me. You have a bad day, you go home and they cheer you up. They were my life.''
He said every one of them had names and different personalities.
"I will never forget.''
During the three-week trial, the court was told Campbell and Mendoza went to shoot the dogs after Mendoza's fox terrier was mauled by a dog they believed belonged to Mr Hargreaves.
Crown prosecutor Joshua Shaw said the men were on a "commando exercise''.
They had a note with them which Campbell got Mr Hargreaves to sign. The note said the men could shoot the dogs and there would be no "comeback''.
Campbell told the court he had not wanted to shoot the dogs but was begged to do it by Mr Hargreaves, something Mr Hargreaves denied.
Judge Sharp described the scene of "pure carnage'' in a cage where eight dogs were shot.
The men were undeterred as the dogs yelped and tried to hide under the bodies of their companions.
Blood stains in the cage indicated some of the dogs bled heavily and moved to other parts of the cage in great pain before dying.
"No person in their right mind would consider it either humane or safe to shoot in a cage with eight dogs moving in it.''
She described the scene when Mendoza brought Campbell dozens of puppies out for them to be executed.
Campbell placed them on top of a steel tray - sometimes on top of the body of a dead puppy - put a knee on their neck and, as he described it, "dispatched'' them.
"It was an inhumane method of dealing with the dogs that I cannot actually contemplate,'' Judge Sharp said.
She found Mr Hargreaves to be a "gentle, if eccentric, man'' who loved his dogs dearly.
He would have been "sufficiently intimidated'' by the two armed men not to intervene in the massacre.
One of those first on the scene was SPCA officer Sacha Keltie, who told APNZ today that she had been "overwhelmed'' when she arrived at the property.
She had struggled to remain focused at the scene as she gathered piles of dead dogs and puppies and took them for examination.
"It was just the sheer scale of it, the number of dogs. There was blood everywhere. I knew I was there to do a job and I knew it was a big case so I just had to be methodical about going through every dog, as horrible as it was.''
Mr Hargreaves said tonight he had new dogs but they would never replace his former companions.
He said the sentence facing the convicted men was not for him to decide but he hoped it sent a clear message about how people treated animals.
"They are not just pieces of meat with four legs and a tail.''
Campbell and Mendoza were remanded at large for sentencing on a date to be determined.
