Illegal and unjustified police harassment, brutality and killing is in no way something new. It has been going on since there were police. In the past it was sometimes conducted by lynch mobs with or without the participation of sworn peace officers. It isn't really necessary for it to be conducted in secret since it is usually fairly easy for police to pass it off as legally justified and in most cases no serious questions are raised. In recent years advocacy groups have become more active in protesting instances of police violence and smart phones have made it easy for bystanders to collect documentary evidence. In Ferguson MO a black community rose up in protest over the killing of a black young man and that has focused the notoriously short attention span of the media on the matter.
Someone passively following the news is likely to get the impression that this is only an issue for black Americans. That is by no means the case. Other stigmatized groups are also vulnerable. A quick Google produces results for fairly recent police killings of Latino men, for example here, here and here.
The forces of structural racism seem to be equally at play with both minority groups. The difference is in the convenient excuses for demonizing the victims as people who deserved what they got. In the case of Latinos immigration status is the primary leverage point. Anybody of Latino ancestry is potentially an "illegal person" without the right to be treated as an American citizen. At this point undocumented migrants have become a fairly small portion of the total Latino population, but that doesn't stop the hue and cry to send them all back where they came from. Harassment over identification and citizenship status is not just limited to Arizona where it has gotten lots of attention. The Southern Poverty Law Center has developed a report on how this particular type of racial profiling has become increasingly prevalent across the south as Latino populations are on the rise there. This is why most Latino political activism is so strongly focused the immigration issue. It is not just a matter of US Latino citizens having concern for their compatriots, but also an awareness of the political utility of using immigration in suppressing the rights of citizens.
Arab Americans and other Muslims are all painted with the broad brush of being potential terrorists. They get subject to the instruments of both immigration and national security. For both them and Latinos the propaganda meme is that they aren't loyal valid Americans, just by virtue of their racial/ethnic identity.
While there are a few black Americans who are recent immigrants from Africa, most of them have native ancestry that goes back to the beginning of the nation. Their citizenship status is not in question and even the black Muslims haven't been featured in the terrorism narrative. Making them the deserving recipients of harassment and brutality requires a different approach. Blacks as a group are characterized as violent law breakers. When an unarmed black man is killed in the name of law and order, there is a mad scramble to to smear him and reach for the implication that he was engaged in a criminal act. Thus we have the claim that Michael Brown was killed because he had stolen some cigars. Trayvon Martin was wearing a hoodie. Even though it was raining that was proof of gang membership. The list goes on.
One of the most effective and enduring tools used by elites to retain power and control is the setting of different sections of the masses against each other. The southern oligarchs retained control by setting poor whites and blacks against each other with the endless insinuation that black men posed a threat to white women. Immigrant groups have long been portrayed as a threat to the economic and sexual security of the dominant population. This is a process that continues to enable police brutality. By painting entire classes of people as perpetual threats, individuals can be abused or eliminated without any serious efforts at legal accountability.