I don't see how there can be any doubt that they are buckling to public pressure, given the last few days' timeline, etc.
I would interpret it as indicative of sloppiness as you said and probably some combination of "good ole boy" network + racism + laziness + benefit of the doubt for former law enforcement / the kind of people who are making an effort to stop crime.
None of which particularly ruffles my feathers, tbh. I'm realistic about how humans are and what's required to make a society function (it isn't always pretty.)
By the way, I find your even handedness, open-mindedness and decision to not just lapse into "duh, you racist and dis was lynching!" to be refreshing and impressive. You appear to be approaching this in a way that actually deserves to be associated with a skeptic / critical thinking forum.