New York City police are asking for the public’s help Friday in identifying a man caught on video repeatedly kicking an elderly woman in the head and body while a crowd of subway passengers look on.

The NYPD says the “heinous attack” happened in the early morning hours of March 10 in the city’s Bronx borough. Footage of it circulating on social media is drawing outrage – not only directed toward the attacker, but to the witnesses seen filming the violence with their cell phones and shouting instead of coming to the woman’s aid.

The 78-year-old woman, who was sitting by herself in the corner of the subway car, is seen in the video holding her arm up trying to stop the man from going after her. At one point, the man grabs onto the subway car’s poles to balance himself on one foot, while using his other to repeatedly kick her in the head and body.

The video ends with the attacker walking out of the subway car while the passengers continue to film the battered woman, who is holding her hand to her face.

Police told the New York Post they were notified of the attack after a bystander flagged an officer at the next stop.

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The newspaper says the woman was treated at the scene for bleeding and swelling, but refused further medical attention. Investigators are now hoping to speak to her again.

It is not clear what provoked the attack, or why the video is only now surfacing, more than 10 days after the attack happened.