It started with a woman asking a man to move his pit bull on the subway, witnesses say, and ended with the dog chomping down on her shoe and refusing to let go.
And between that, there were some punches thrown, witnesses told NBC New York.
TahSyi Kyng, who recorded as the dog continued to bite down on the 22-year-old, said "it just happened so fast."
He told ABC7 that the man walked onto the subway train at around 4 p.m. Friday and then put his dog on a subway seat.
But the woman, who had already been sitting in an a nearby seat, didn't appreciate having the pit bull so close to her, Kyng said.
"She was like, 'The dog don't belong on the seat, that's an animal. People belong on the seat, put the dog on the floor,'" Kyng told ABC7. "And he looked at her like, I'm not moving my ***ing dog.'"
Denise Leon, Kyng's girlfriend who was also on the subway, said that the woman continued to push the dog off the seat as the owner continued to warn, "Don't touch my dog."
"She does it again, does it again. This is three times," Leon told NBC New York. "The third time, he leans, punches her right on her face. She seen it coming because she hit him back."
Then the pit bull chomped down on her shoe — and wouldn't let go.
"She tried to kick it, so thank God it was her sneaker it caught on to," Leon said to NBC New York.
Kyng recorded it and shared the footage on Facebook.
In the video, the dog's owner can be heard yelling "she attacked him first" as his pit bull continues to keep its jaw tightly locked on the woman's shoe.
"Call the police!" one person suggests as multiple passengers try to remove the dog.
"You're going to jail," another man says as he records the incident. "And he's gonna get euthanized."
The dog eventually rips off the shoe and the man is seen throwing it back at the woman.
The New York Daily News reached out to the Metropolitan Transportation Authority, which said it will provide the video to the New York Police Department. The MTA said it isn't sure of the location or date of the incident at the moment.
“Our rules require non-service animals to be kept inside containers and not disturbing other passengers,” MTA spokesman Shams Tarek said. “What’s happening in this video is disturbing and a clear violation of our rules.”
Kyng told CBS New York that everyone had to get off the train at the next stop. That prevented him from checking on the well-being of the woman, whom he said didn't appear to be bleeding.
Leon praised other passengers on the subway for their quick action.
"Because sometimes we don't stick up (for others)," she told ABC7, "but that was a moment where everyone stuck up for her."
But Kyng argued that the dog's owner could have prevented it all.
"You should've had your dog in a bag, kennel, muzzle," he told NBC New York. "It wasn't a service dog."