I was walking with my teenage godson in Miami Beach, Florida, last year during spring break when a police car turned on its flashing lights and sped toward us. My godson took off running and then stopped 20 yards later, turned around and laughed.

Once the police car drove by us, I lost my temper. "What are you doing?" I yelled. My godson's smile quickly turned to horror. He could not understand why I was so mad.

"Don't you know that young Black men get shot and killed for doing that?" I told him. "If you ever see a police car coming toward you, do not run away. That's just going to give them an excuse to come after you."

I felt sorry for yelling at him, and I apologized for my tone, but I stuck by my words, even as he looked at me as though I was some sort of relic from the civil rights museum. I could tell he didn't fully believe me.

My godson is a good kid with a 3.7 GPA in his senior year of high school. He attended a mixed suburban school where kids of all races got along relatively well. Like many young Black suburban kids, he had not been directly exposed to the harsh reality of racial injustice in America.

So when I heard the news recently that an innocent, unarmed 17-year-old Black kid had been shot and killed in Florida by a white vigilante, I immediately thought of my godson.

All Trayvon Martin wanted to do was to play football and become a pilot when he grew up. But one day in February, as he was walking down the street of a mostly white neighborhood on his way back to his father's house, he was confronted by George Zimmerman, a local neighborhood watch captain who suspected Martin of engaging in "suspicious" activity.

Martin had just come from the store, carrying a bag of skittles and a can of Arizona iced tea, but Zimmerman assumed the young Black kid must have been a criminal. Despite reportedly being told by 911 operators to let the police handle the situation, the 28-year-old Zimmerman got out of his SUV, pulled out his 9mm semi-automatic handgun and fired a shot that killed the young Martin.

The 200-pound, 28-year-old Zimmerman, who had previously been arrested on charges of battery on a law enforcement officer and resisting arrest with violence, told police he was acting in "self-defense" when he shot the unarmed 140-pound Martin. But here's the shocking part: The police believed it. "We don't have the grounds to arrest him," Sanford, Florida, Police Chief Bill Lee told reporters.

Are you kidding? Imagine a slightly different scenario. If a 28-year-old Black man shot an unarmed white teenager in Florida, do you really think the Black man would still be walking free?

I went to high school in Florida years ago in a mostly white suburban community. Once I got my driver's license, I rode my Yamaha motorcycle to school every day. Although local rednecks yelled the N word at me a few times back then, I don't remember ever feeling my life was in danger. Maybe I was just as naive as my godson as I moved through my suburban world assuming I was safe, but that's what kids do.

The role of the police is to protect and to serve us. So when a vigilante can gun down an innocent civilian and the police simply take his word for it, law enforcement violates its trust with the citizens it's sworn to protect.

The investigation into the killing of Trayvon Martin has recently been turned over to the State Attorney’s office, but even if the state finally files charges, a larger question remains: Why should young Black boys feel as though their lives are endangered every time they walk out the door?

Even with a Black president and a Black attorney general in Washington, we still live in a society where young Black males are far too easily vilified and demonized, and sometimes killed.

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Keith Boykin is a New York Times best-selling author and former White House aide to President Clinton. He attended Harvard Law School with President Obama and currently serves as a TV political commentator. He provides political commentary for BET.com each week.