"A week or two later we were chatting with our neighbour who had just been away and he told us that his two cats had been shot while he was away.
"It wasn't until then that we clicked and realised what had happened."
The same had happened to Blue who had been shot, with the metal slug still in her neck.
"We took her to the vet and they cut it out and confirmed that it was a metal slug sitting in there.
"She was shot first a couple of weeks before the neighbour's cats, but we didn't know that that's what had happened until a few weeks later.
"Because it had happened to three cats, only two of which survived, and after the vet said they had other similar cases, I posted on social media to make others aware of the problem.
"It's just really nasty. It's not fair and I just want to make others aware of what's happening and see if anyone knew anything about it."
After talking to the vet who suggested lodging a formal complaint with the SPCA, Hannah did just that so that the SPCA could begin an official investigation.
"They've been really good, taking it seriously and looking into it further."
After finding out that there was still a slug in Blue's neck Hannah and her partner got it removed and gave the slug to the SPCA to take away as a sample.
SPCA communications manager Jessie Gilchrist said the society couldn't comment on the investigation but it is an isolated incident.
"Causing an animal unnecessary pain and stress is an offence under the Animal Welfare Act."