People block a path during a Black Lives Matter protest outside City Hall in Manhattan, New York, U.S., Aug. 1, 2016. Reuters

Alfred Olango, 30, became the latest mentally ill person to be killed by police after a San Diego police officer shot the unarmed black man Tuesday night in the El Cajon suburb in California. His death sparked protests in the region amid an ongoing debate over police brutality and the Black Lives Matter social justice movement's call for reform.

Police confronted Olango at a local strip mall after his sister called 911 to report that he was acting strangely. "Why couldn't you tase him? I told you he is sick. And you guys shot him!" Olango's sister can be heard telling officers in a video of the shooting. "I called police to help him, not to kill him."

El Cajon police chief Jeff Davis told reporters Olango refused to put his hands up in the air and at one point seemed to pull an object from his pocks and point it at officers in a "shooting stance." But local news agency CBS8 reported that "several witnesses alleged that the officers were unduly quick to open fire and suggested that their actions had been influenced by the fact that they were dealing with a black man, one they described as mentally challenged."

Olango is the 217th black person killed by police in the United States so far this year, according to the Mapping Police Violence research project. Black Americans are about 3.49 times more likely to be shot by police compared with white Americans, according to a study by a University of California, Davis professor. Black Lives Matter activists claim law enforcement officials too often shoot to kill, especially when interacting with black Americans.

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Olango is also not the first person with mental problems whose family called 911 asking for help only to see their relative killed. A Washington Post analysis in 2015 found police officers killing black men made up only 4 percent of fatal police shootings. Instead, police officers were more likely to kill someone because they were suicidal or mentally troubled.

"Officers fatally shot at least 243 people with mental health problems: 75 who were explicitly suicidal and 168 for whom police or family members confirmed a history of mental illness. The analysis found that about 9 in 10 of the mentally troubled people were armed, usually with guns but also with knives or other sharp objects. But the analysis also found that most of them died at the hands of police officers who had not been trained to deal with the mentally ill," the Washington Post noted.

"Often they have an edged weapon, like a knife, and when officers start yelling, ‘Drop it! Drop it!’ that will not calm them down," Chuck Wexler, executive director of the Police Executive Research Forum in Washington, told the Post. "Instead, it increases their anxiety."

In March 2015, the Department of Justice released its investigation into the behavior of police in Ferguson, Missouri, after the death of 18-year-old Michael Brown, a black man who was unarmed. "Officers expect and demand compliance even when they lack legal authority," the report’s authors wrote. "They are inclined to interpret the exercise of free-speech rights as unlawful disobedience, innocent movements as physical threats, indications of mental or physical illness as belligerence."

Roughly 8 million Americans suffer from a serious mental illness. They are generally not violent, but often end up interacting with police officers over minor offenses, such as loitering, shoplifting or urinating in public, said John Snook, executive director of the Treatment Advocacy Center in Virginia, which has studied police killings of people with mental illness.

"What we need to do is treat the person before the police are ever called. This is a mental illness, but we respond by calling the police and arresting a person," he told USA Today.