Where do black girls learn this?

I am a 70-something white male.

I never, ever, heard of bashing someone's head into concrete pavement, until they either die or suffer permanent traumatic brain injury.

As a white male, I just can't imagine doing that.

What a barbaric act.

But now let's look at reality, what some young black women have done.

First, a homicide:

https://mpdc.dc.gov/release/mpd-arrests-additional-teenagers-northwest-homicide

Second, the head bashing causing permanent brain damage.

https://youtu.be/wdSn6doB2_A

I don't think there can be any excuse whatsoever for such acts.

And in my 1950s era white culture, I don't think that could have ever been explained.

Such acts were simply inconceivable.