A hedgehog had to be put down after a firework was attached to its head and set off.
The animal was targeted on Friday evening in Pendlebury Close, Longton, Lancashire, South Ribble Police said.
Posting on Facebook, the force added it was with "great sadness" the hedgehog had to be put down "due to the extent of its injuries".
Officers have asked any witnesses or anyone with information to get in touch.
An RSPCA spokeswoman said she was "extremely concerned to hear about this horrific incident".
"Sadly we do receive complaints about people misusing fireworks to cruelly target pets as well as wildlife," she said.
"If someone has deliberately tied a firework to a hedgehog we would urge anyone who knows the person responsible to either call the police or the RSPCA", she said.