It sucks, but women of all races are assaulted and murdered by abusive intimate partners all the time, for reasons stemming from the abuser's own pathology. Socioeconomic factors can play a role, and the easy availability of firearms in this country doesn't help, but men who do things like this do them because they have a screw loose in their own brains.
In other words, I don't think this has anything directly to do with this women being black or with shutting anyone up.
The most likely scenario is that she had recently left him. The period after leaving an abusive partners is a perilous time (see the link below). The fact that he shot her as she was leaving her workplace also points to that. I'd bet money he laid in wait for her to come out of the building so he could ambush her.
Private Violence: up to 75% of abused women who are murdered are killed after they leave their partners
There is a toxic question that surrounds abused women: “why didn’t she just leave him?”
The answer, too often, is that many women that do leave get killed.
“The thing that I did not know that was so revealing to me was that anywhere between 50% and 75% of domestic violence homicides happen at the pointm of separation or after [the victim] has already left [her abuser],” says Cynthia Hill, director of HBO’s Private Violence.
More here:
https://www.theguardian.com/money/us-money-blog/2014/oct/20/domestic-private-violence-women-men-abuse-hbo-ray-rice (Note: This is an old article, but the basic facts haven't changed.)
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