The RSPCA is appealing for information about a video shared on Snapchat showing teenagers apparently beating a duck to death with a baseball bat.
The video is believed to have been shot in the York area and appears to show a duck being thrown into the air while someone else swings a bat at it.
Later, it cuts to a clip of the animal being hit on the head, captioned with the words "Ducks life matter".
Insp Thomas Hutton, from the charity, said it was "extremely distressing".
The video, which first came to light in July, "shows two teenagers carrying out an awful act of violence against a poor, defenceless duck", Mr Hutton said.
"The attack was then posted on social media platform Snapchat, which is popular with children and young teenagers, and it is particularly troubling that they could easily have witnessed this act of brutality through their phones."
He said the charity, which has only released a still image from the footage, wanted to hear from anyone with information about who was responsible for the attack.
It said any information received would be dealt with in the "strictest confidence".