A cat was killed when a firework which was strapped to its back exploded.
Northamptonshire Police have launched an investigation after the incident was reported by a woman who witnessed the blast with her daughter in Shelley Road, Wellingborough, just after 6pm on Saturday.
A force spokeswoman said the firework exploded, resulting in the cat's immediate death.
The cat's owner, who lives in the street, has been notified of the incident, she added.
Pc Mark Jones said: "This is an unbelievably cruel act and we are very keen to hear from anybody who has any information which will lead to the identification of the perpetrators.
"Not only was it horrific for the poor animal involved, the witnesses and owners of the cat are understandably very distressed.
"I urge anybody with any information to get in touch so that we can identify and deal with whoever is responsible for this horrible act."
Anyone with information on the incident can contact Northamptonshire Police on 101.