They had injuries consistent with being hit on the head, Mr Shieffelbien said.
"It makes me angry and sad that this is happening. Animals shouldn't suffer."
None of the cats had identification tags so he removed them from the park and disposed of them, unable to contact owners.
"I didn't want children going to the park and seeing that, and they were starting to smell, so I wrapped them in plastic bags and put them in the bin."
Mr Shieffelbien, a security guard, said he did not report those incidents because he did not think there was anything anyone could do.
But finding his own cat, which went missing last week, prompted him to act.
His partner Pat McKean's cat Missy was also found in Navy Park with its throat slit late last year.
"There is definitely someone in the area killing them. Before Christmas quite a few pet cats were found dead lying in gutters and things like that. Then it died down, but now too many cats have been hanged to let someone get away with it."
Mr Shieffelbien and Mrs McKean were keeping their remaining cat - Chilla - and two of its 8-week-old kittens safely indoors.
Senior Constable Ruth Parsons, of South Dunedin, was investigating the alleged cat killings and urged anyone who witnessed suspicious behaviour in the area to contact police.
SPCA Otago inspector Julie Richardson was "sickened" by the cat hangings and also encouraged anyone with information to come forward.
Ms Richardson said the cat deaths would be reported to the SPCA's national office, which had requested any information about cat cruelty since widespread coverage of Gareth Morgan's anti-cat campaign.
Those convicted of wilful ill-treatment of animals could be sentenced to five years in jail and made to pay a $100,000 fine.
The Dunedin City Council had not received any reports or complaints in relation to the cat deaths.
Aggravated violence and cruelty against cats is on the rise in New Zealand, significantly since late January when Gareth Morgan launched his anti-cat campaign, SPCA national president Bob Kerridge says.
Mr Kerridge asked staff at all SPCA branches to collate information about cases of cat cruelty following widespread media about Mr Morgan's campaign, to identify whether it led to an increase.
"I was concerned that the campaign may well trigger an impulse in some people who have a dislike of cats to actually take that dislike out on them. As a result of that we've had reports of some bizarre cat cases."
Dead cats found hanging from trees in a South Dunedin park recently was one such example and the result of a "very sick and vindictive mind", Mr Kerridge said.
He did not directly link cases of cat cruelty to Mr Morgan, but said the campaign's negative impact was noticeable.
"We've had sufficient evidence to suggest that in the last few months there has been an increase of incidents against cats."
Mr Morgan said it was mere speculation his campaign prompted people to be cruel towards cats, and under no circumstances did he support or endorse cruelty towards any animal.
The SPCA had a vested interest in linking his campaign to an alleged increase in cat cruelty, he said.
"It's an irresponsible organisation, taken over by animal rights people, who put the rights of cats over the rights of any other species. I've told the SPCA, publicly and privately, that I'll become their biggest supporter - financially and morally - once they retain their moral compass and stop supporting stray cats," Mr Morgan said.
