Protesters against police violence march towards the White House in Washington, April 29, 2015. [Photo/Agencies]

A new wave of anger has swept across the United States following the death of Freddie Gray in police custody in Baltimore, Maryland. The 25-year-old African American was detained for illegally possessing a knife. While being transported in a police van, his head collided with the back of the vehicle, leading to serious injury to his neck and eventual death.

As US President Barack Obama has said: "The key is to find (the) truth (in this incident)." He has also said that the trend of African Americans dying at the hands of police has become "a slowly developing crisis".

The quick response of the Baltimore prosecutor seems to have added to the public fury. Based on initial findings, Gray did carry a knife but not the type that is banned. Also, the six policemen who handled Gray's case have been found responsible for his injury and death, and indicted on criminal charges.

Further investigations into the case and the legal process to punish the guilty could take a long time. And although it is abnormal that so many African Americans have died at the hands of police officers, it is technically challenging to find evidence to prove the criminals charges, especially because police represent the government.

No wonder, Gary's case has again aroused Americans' awareness of racial discrimination and raised tensions. On a larger scale, this phenomenon has been a part of American society. Though human rights in the US have greatly improved since the civil rights movement half a century ago, America is still not free of ethnic inequality.

The absurd rate of African Americans dying at the hands of police officers has its reasons. One such reason is the excessive power police officers exercise at will. Since police enforce law, they can easily abuse it too by resorting to excessive violence, if their actions are not checked. That's why a growing number of American people are demanding that police be monitored while on duty to protect them from being victimized as well as deter them from victimizing others.

For years, American police officers have been suspected of disposing their cases high-handedly, and using their firearms excessively, even unnecessarily. But it was hard to find on-the-spot evidence of such acts until a video footage of the shooting of Walter Scott, another African American, in South Carolina was revealed last month. Michael Slager, the policeman who shot Scott eight times, is now facing murder charges.

The other reason why American police have targeted African Americans has a lot to do with the lukewarm response of the country's media. The US media have preached fairness and equality for long and some outlets indeed have stood up for social justice. But, facing the persistent disease of police abusing African Americans, the media outlets have been largely tolerant of the police violence.

The US is closer to realizing the dream of Dr. Martin Luther King, Jr., and the dark page of racial segregation is truly history. However, cultural separation is far from over. The distance between the government and the colored people, and even that among African Americans themselves, has not been bridged. For many, the American Dream is still quite distant.

Despite the specter of racial discrimination haunting the US, the American administration and media continue to criticize other countries' for their so-called human rights record. Sure, a country need not be an epitome of perfection in every field before criticizing others. But it makes sense to first set one's house in order before judging anyone else. It's time the US started looking inwardly and fixed its domestic problems, especially the abuse of African Americans.

The author is a professor and associate dean at the Institute of International Studies, Fudan University, Shanghai.