> Why is this happening?

This specific case, I would bet dollars to donuts, happened because: (1) The administration is hypersensitive in light of the wave of race related protests and associated two-sided violence occurring in the country. (2) Someone aware of the likelihood of that deliberately trolled the administration, probably under a false flag, to produce an incident.

Possibly just for lulz, more likely than that in the hopes of benefiting a particular domestic political faction, but even money it was done on behalf of (though not necessarily at the direction of) a foreign power.