I'm not qualified to determine whether the guy's science is sound or not, and I damn sure don't endorse "shoot first and ask questions later." But I've been the guy with dirty boots carrying a gun and can tell you that unless you've been there, it's difficult to understand how quickly things happen and how your brain and nervous system react...far too quickly to rationally consider things like "he is shooting too fast to have a high probability of hitting me" or "statistically my job is not getting more dangerous" like so many enlightened internet commenters are proposing. Comments like that nauseating naiveté masquerading as enlightenment, not constructive solutions to police shootings.
Let me state unequivocally that one preventable death is too many, regardless of race or circumstance, and police officers who abuse their power or hide behind their badge ought to be punished more harshly given the increased responsibility they bear.
But in the same way that we ought to empathize with the victims who have gotten the short end of the stick from our justice system and society in general, maybe we ought not to be so quick to judge officers who do a dangerous and often thankless job, but one that's critical to society. Especially those who have never been in a shoot/don't shoot situation or faced the ambiguity of trying to determine in the heat of the moment whether the situation unfolding before them in real time is truly a shoot/don't shoot situation.