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Diamond Reynolds, the girlfriend of Philando Castile of St. Paul, cries outside the governor's residence in St. Paul, Minn., on Thursday, July 7, 2016. Castile was shot and killed after a traffic stop by police in Falcon Heights, Wednesday night. A video shot by Reynolds of the shooting went viral. (AP Photo/Jim Mone)

Philando Castile was shot to death by a St. Anthony, Minn., policeman on Wednesday, reportedly during a routine traffic stop for a "busted taillight." Castile, a 32-year-old school cafeteria worker who apparently had informed the officer he had a legal permit to carry a firearm, was in the car with his girlfriend and young daughter. Castile's girlfriend live-streamed the aftermath of the shooting.

"Police just shot my boyfriend for no apparent reason," the African-American woman said as the officer continued to point a gun into the car.

"I told him not to reach for it. I told him to get his hand out," the officer said.

"You shot four bullets into him, sir," she replied. "He was just getting his license and registration, sir."

The tragedy comes on the heels of the fatal police shooting in Baton Rouge, Louisiana, of 37-year-old Alton Sterling while officers struggled with him on the ground. This shocking shooting also was videotaped by witnesses.

Outrage and horror over the shootings have spread rapidly across the country and the world as the videos have circulated.

Why have there been so many police killings of black men in recent years that an activist group focused on stopping police violence, Black Lives Matter, has come to prominence in American politics?

African-American comedian D.L. Hughley fears he knows the answer. Our children and parents and friends are "brutalized and nobody says anything," he said on CNN Thursday, his eyes welling with tears. "It's too much. It's too much."

Hughley later posted to Facebook an article published last year by law professor and former military police captain Samuel V. Jones. The article refers to a 2006 FBI report that warns of a concerted, decades-long attempt by white supremacists to infiltrate law enforcement.

"[T]he term 'ghost skins' has gained currency among white supremacists to describe those who avoid overt displays of their beliefs to blend into society and covertly advance white supremacist causes," the FBI report states.

There is no evidence that the officers involved in the St. Paul and Baton Rogue shootings have any ties to white supremacist groups or hold racist views. Official investigations will determine whether the shootings were justified or not. The frequency of such incidents, however, suggests at the least that commonplace cultural attitudes about class and race make police stops very dangerous for young black men. And the 2006 FBI report argues that sometimes there are even worse motives at play.

"Several key events preceded the report," Jones wrote. "A federal court found that members of a Los Angeles sheriff's department formed a neo-Nazi gang and habitually terrorized the black community. Later, the Chicago police department fired Jon Burge, a detective with reputed ties to the Ku Klux Klan, after discovering he tortured over 100 black male suspects. Thereafter, the mayor of Cleveland discovered that many of the city police locker rooms were infested with 'White Power' graffiti. Years later, a Texas sheriff department discovered that two of its deputies were recruited for the Klan."

For many white Americans, the typical policeman of their imagination remains the one that the late illustrator Norman Rockwell made iconic: the kind, dedicated, soft-hearted man of the community. And that officer certainly exists in police departments across the country. But for black Americans, as expertly showcased in the recent ESPN documentary about the OJ Simpson murder case, the reality of policing in the U.S. is very different. Last year, another African-American comedian, Chris Rock, posted to social media several photos of him being stopped by police. In one post, he wrote: "Stopped by the cops again -- wish me luck."

Stopped by the cops again wish me luck. pic.twitter.com/6t0wlgwkrJ — Chris Rock (@chrisrock) March 31, 2015

Reacting to Jones's piece about white supremacists in law enforcement, New Orleans Times-Picayune columnist Jarvis DeBerry last year reminded readers of Michael Elsbury, a white Baton Rogue police officer who resigned after "he was linked" to racist text messages.

"I wish someone would pull a Ferguson on them and take them out," Elsbury reportedly wrote in one message, referring to the 2014 police shooting of Michael Brown. "I hate looking at those African monkeys at work ... I enjoy arresting those thugs with their saggy pants."

DeBerry worried that officers like Elsbury are not unusual. "Would a police officer with such white supremacist views even stick out?" he wrote. "Or are anti-black hatred and standard American policing so similar to one another that we wouldn't notice anything remarkable about a black-hating cop on patrol?"

Those are distressing, inflammatory and probably unfair questions to ask, but they are questions that are increasingly being asked by Americans of all colors.

-- Douglas Perry