Long term effects of screaming at an infant to shut the fuck up

This may be a bit long, so I apologize

My son is 4. My mother in law watched him when he was an infant while I worked two days a week. On those days, she also watched her other grandchildren, who were older when they got out of school.

I never liked the idea of her watching my son, my mother in law is a very high strung stressed out person. Plus she ultimately stopped watching him when she was crossing boundaries, but that’s a whole other story. My son went to daycare the other days I worked, and he loved it there so I wanted him there full time. But she was very adamant she wanted to watch him too, so they could bond.

Anyway, over the weekend, my niece and nephew were over. They were the other two kids my MIL watched while my son was there. They are now 13 and 15 years old.

I don’t know how we got on this topic, but they started talking about how crazy their grandma is. My nephew said to my niece “remember how when *my sons name* would cry and she would start screaming shut the fuck up? And my niece is as like “oh yeah, and she would yell get this fucking baby away from me” I was like 🤯🤯🤯 please explain to me what went down and they told me that she would pick them up from school, get home, and start cooking. She would get stressed out if my son started crying and go off screaming at him, screaming “I can’t watch this fucking baby anymore” and my niece and nephew thought ir was “funny how crazy she got”

I have no doubt watching 3 kids while trying to cook dinner is stressful. I definitely get stressed out when I’m cooking. But the thing that’s bothering me is I constantly told my mil if it was too much she didn’t have to watch him, like he was already in daycare, adding two extra days wouldn’t have mattered.

I feel guilty because I know how my MIL is. I have seen her flip out a million times, I just never thought my son would be the target of her anger.

And she stopped watching him when he was ten months old. So he was a little baby when this all went down.

I’m worried he will have long term effects? I always read how screaming at a baby can have detrimental effects. Since my son was taken out of the situation at ten months old will he be ok?