You have confused the definition of “racism“ with “systemic racism“. A person, or a group, can be victims of racism without that racism having any realistic effect on them. Such is the case in South Africa. In cases, such as this, it is often a consequence of the actions of said group.
Which, of course, feeds into prejudice. And prejudice isn’t always unjustified. Again, as with the white people in South Africa, they certainly earned that prejudice through generations of colonization and apartheid.
The police certainly had this coming, although I now feel very bad for firefighters and teachers in Utah