I'd tend to think that BLM is more likely to be a symptom, not a cause.
And yes, a 20% increase in homicide rates over 2 years is extremely significant.
I'd want to see the details. Can we get any more specific than just 'homicides' in general?
Is the violence in the cities, or generalized out? Affecting specific ethnicities specifically? Gang violence or domestic? Is it more first degree(planned) or 2nd degree(spontaneous)?
Can it be accounted for by standard known variations like the economy? Hell, were we releasing a bunch of prisoners with lead damaged brains?
Roughly speaking, data mining to find the factors that are associated with the extra violence. I'm learning how to do that right now.