The woman who was lying on the ground is eventually helped onto her feet, with blood pouring from her head and face.
The woman being kicked was later identified as Bianca Bouchard, 21, who is 15 weeks pregnant.
Bouchard was at the graduation to support her sister's boyfriend, and said she didn't know the woman who kicked her, but it was over a "family feud."
"My sister fought one of the girls who was graduating," Bouchard told the New York Post.
She said she got caught up in it all while she was trying to defend her younger sister.
Loronzo Saez, 20, filmed the vicious brawl, which eventually spilled out into the school's parking lot and posted it to Facebook.
Saez called the fight "crazy," and said security did try to break it up, but "they weren't doing a good job."
In the footage, one of the guards can be seen trying to restrain a shirtless man, who seemed to be defending one of the people involved in the fight.
Suffolk county police were called to the incident around noon, but the fight had already been broken up by the time they got there, a spokesperson said.
The William Floyd School District released a statement condemning the fight, saying: "We are disappointed by the actions of those who instigated the incident on what was a joyous occasion for our students and their families."
The statement also said district officials will be pressing charges, though no arrests were immediately made.
