Based on how the execution was carried out, and the noncholant, overconfident behaviour of the murderers immediately after the killing, I think it's highly probable that ICE thugs have been briefed that they are free to use deadly force against any protester in possession of a firearm.
Hence the immediate response of riddling the victim with bullets in the back, once his holstered weapon became visible as he was struggling on the ground. America being America this isn't going to result in fewer protesters turning up armed. This may get very bad, very fast.