The video went viral on social media, causing an uproar in the dog-loving community.
In the video, you can see the man walk up to the Bordeaux mastiff, who was sticking his head out of the back window of a black pick-up truck.
The man puts his hand out to the dog as if heโs pretending to give him food. Instead, after a few seconds, he slaps the defenseless dog across the face, hard enough to hear the hit out loud from quite a few feet away.
The exact location of the incident is unknown, but investigators believe it may have been somewhere in the United Kingdom, since many passing cars had UK license plates.
Investigators are now asking the public for help in tracking down the suspect.
The man is white with light-colored hair, and was wearing a white, long-sleeve shirt, black trousers, and shiny black shoes.
If you recognize this man or have any information, please contact the RSPCA appeal line at 0300 123 8018.
Watch the sickening incident in the video below:
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