A 12-year-old girl was punched and kicked while she lay helpless on the ground.
Ellie Hussey was walking in Bransholme, near Hull, on the east coast of England, with her 13-year-old friend, who captured the attack on video.
The video shows two adult women bashing the young girl, but it is believed a third woman was also involved, reported news.com.au.
The footage was posted to Facebook, and Ellie's father Mark Hussey was shocked by the brutality, which police are now investigating.
Mr Hussey told the Mirror Online the footage "sickened" him.
"It makes you feel sick to see that as a dad. Kids get into scraps but when it's three adults against a child that's a different league," he said.
"She had a couple of marks on her face but it was more how it shook her up. It's not right and my heart just broke seeing what had happened.
"If I was the father of one of the others I'd feel ashamed of what happened and apologise straight away."
Mr Hussey wants to video to be shared on Facebook so people can see how wrong it is and ensure it doesn't happen again.
The Mirror Online reports Humberside Police confirmed an investigation into the attack that happened about 3.30pm on April 14.
"Our inquiries are ongoing and initial reports indicate that although shaken by the incident, the 12-year-old girl had no visible injuries."
The Hull Daily Mail reports Ellie knew the women who attacked her, and were believed to be aged between 18 and 21.
The young girl said she was slapped then held down while another girl punched and kicked her.
Ellie was also dragged across a path during the ordeal.