Young American mother with child brutally attacked by 2 young women in park

This is a video of a young American mother attacked by 2 young/teenage women in a park. The video shows the woman pulled off a bench by her hair, dropping her baby and getting punched and kicked by the 2 women. Her baby is watching the attack and crying. Nobody stops it, and a young male is dancing around the attack as it happens, he appears to be excited by the violence.

The motivation for the attack, the exact location and names of the people involved are unknown.