The incident happened on Bloomfield Avenue in Montclair last Wednesday.
The video, taken by two people in a car behind the two vehicles involved, shows two men fighting in the street. After an older man punches and shoves a younger one while shouting profanity, the younger man pulls the dog from the older man's passenger seat and throws it on the sidewalk.
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He then gets in his car and drives off.
Authorities say the dog is recovering and was not seriously injured.
It is unclear what led up to the argument, but police say they have spoken to both parties involved in the altercation.
Montclair police said the New Jersey SPCA and local Montclair Animal Control have taken over the investigation and would be the one to pursue criminal charges as they deem appropriate.