May 28 2019 Park Slope Play Ground at 3rd st and 5th ave - bad nanny!

I am a nanny, I have never before thought badly of another nanny, I was not sure if I should say something, but I am going to do so. I and other nannies and mothers witnessed this and felt concerned.  I have a video of the nanny and child leaving the playground but not the incident, I will attach the video. There was a boy, about 5 years old screaming hysterically while being draped over the nannie's lap facing up laying like a baby. The nanny was sitting on a bench and had a friend sitting to her left and another nanny standing to her right. The two on the sides were kind of huddled together as if they were trying to hide what the nanny was doing.
 And the one standing was kind of looking around at times to see if people were looking but none of them offered any kind of explanation or assurance that things were OK, despite the child hysterically screaming

It looked like the nanny had a hard blue ice pack and was holding it forcibly to the child's mouth as he screamed "no" and fought to get away. The nanny standing to her right started holding the boys legs so he could not kick. It felt very wrong but I thought they must need to stop bleeding or something and do what was in the boys best interest  even if it hurt him, BUT - I got closer and I saw no reason to hold him down like that, hard and hurtful. Later, the nanny sat the boy up rather roughly and aggressively  like she was angry (making me think she did not think she had his best interests at heart) and shook him once and said "stop it!" At that point,I decided I should film them leaving.

The boy is light skin with turquoise shorts and a whitish shirt and the nanny is darker complexioned  in her late 30's or older, she has a blue bag.

I am a nanny, I know how this goes, I wish to speak with any care giver or the mom thru I saw your nanny, I wish to speak with the mother