BOSTON (CBS) – Video of a brutal beating on the Red Line went viral, and the man who shot it is coming under fire for not stepping in.

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Watch Video Here (Warning: explicit language)

Last Thursday night as the train approached Park Street, a woman accused a man of stepping on her dog’s paw and then made good on her threat of violence, punching the man several times in the head.

Tim Antonellis shot the now-infamous video.

WBZ NewsRadio 1030’s Karen Twomey got reaction from other commuters on Monday:

He was heard laughing in the background as he shot the video on his cellphone, and posted it on YouTube. Social media has been full of people questioning why he did not step in.

“You’re not gonna take a swing at some crazy person on the train, and me, I’m not gonna jump in the middle of something like that and probably get myself hurt,” said Antonellis. “I got a video of it. It’s probably gonna help catch her.”

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In fairness, no one else stepped in during the initial beating, although one man did finally pull the woman off, ending the attack.

After the assault, witnesses said the suspect got off at the Park Street station.

Antonellis says he laughed because he knew the victim was not seriously hurt, but he hopes his video helps.

“This woman needs some help. I mean, either way, she’s got some issues if she’s taking a swing at someone on a train in the middle of rush hour,” said Antonellis. “So if it gets her some help, that’s gonna be the best thing about it.”

Tim Antonellis witnessed the beating and recorded it.

Antonellis said he thinks he has seen the woman on the train before. What if he saw her on the train again?

“(I would) cover my face and hope that she doesn’t recognize me,” said Antonellis.

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Witnesses said the victim was not seriously hurt and does not want to press charges. But, police said the woman could face a charge of disorderly conduct.