The SPCA plans to proceed with charges against people involved in the killing of 33 dogs last week.
The animals were shot dead at a rural property near Wellsford, north of Auckland.
The animal welfare organisation says an investigation has indicated that number of the dogs and puppies suffered throughout the ordeal.
A witness says the animals were screaming in fear during the 20 minutes of frenzied shooting, while the SPCA says it is a frightening example of animal abuse.
Auckland SPCA executive director Bob Kerridge says it has yet to determine exactly what charges will be laid in relation to the shooting.
At least two men have been accused of being involved in killing the dogs and puppies.
Mr Kerridge says it is too soon to say exactly who will be charged, but the owner of the dogs is not being investigated.
"The owner of the dogs, in our regard, has not caused any particular problems, we've had reports on that.
"The investigation is certainly related to how did those animals die, did they suffer and if that's the case, charges must be laid."
Mr Kerridge says in his many years with the SPCA, there has never been an atrocity against animals on a scale such as this. He says the SPCA is waiting on test results and information from police, who are also investigating.
The SPCA says it could be at least a month before it lays charges.
Meanwhile, the lawyer for one of two men accused of the shootings says his client only shot one dog at point-blank range and did so under the supervision of someone with a firearms licence.
