A fly-blown lamb was left outside the Wanganui Toy Library last week and was in "complete shock" when staff went to help it.
Staff member Rose Woon thought the animal was half burned and had a wound on its neck with maggots inside. SPCA staff said it was not burned, but fly-blown.
"We turned up and a very sick and injured lamb had been put in our little fenced area," Mrs Woon said.
They found the lamb on Thursday morning with a bit of hay, unable to move, she said.
"We're, like, right next to the SPCA. I'm assuming they couldn't get it over the fence, they just left it there."
She described the lamb as being in "complete shock".
It has since been put down, SPCA staff say.
"They left it on a day where we were due to open half an hour later," Mrs Woon said. "I'm just really, really grateful that we got there to clean up before all the kids started turning up."
The SPCA would not comment further on the lamb as they said the information was confidential.