What a mess.
I have a nephew who is of Portuguese descent. If he had been standing on the train next to the dead suspect, he probably would be dead, too. He is just one camel short of looking like an Arab.
Oh yes. This is going to cause some serious problems. Not the sort of cock-up one wants to see when the police need to keep good morale and the public at large need to trust their competence. Shooting suicide bombers repeatedly in the head at close range is still a perfectly valid tactic, but if you're going to do it then it's helpful not to get sloppy in identifying a suspect and assessing what threat they pose.
Shooting random Brazilians for being brown and suspicious-looking isn't very smart or good for the public's morale.