There's an undeniable racial component, yeah, but there's also the very real fact that those suffering past abuses were broadly in a different category from the majority of ordinary (white and white passing) American citizens, creating the illusion that they themselves were safe, or could choose to be safe by keeping their heads down.
As soon as the victim is in a position that you yourself could easily find yourself in (like dropping your kid off at school in a residential area), and you can imagine that you might make the same choices (like trying to leave a dangerous situation safely), your own safety is under direct threat.
A lot of people were sad, angry and outraged before, but now they're scared.