MICHEL MARTIN, HOST:

There is no dispute about one thing. It's been a terrible week starting late on Tuesday night in Baton Rouge, La.

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UNIDENTIFIED OFFICER #1: Get on the ground. Get on the ground.

MARTIN: Thirty-seven-year-old Alton Sterling was shot to death by police outside a convenience store. His dying moments were captured on video and sparked outrage.

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UNIDENTIFIED CROWD: (Singing) No more tears crying. No more tears crying.

MARTIN: One day later...

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DIAMOND REYNOLDS: He just shot his arm off. We got pulled over on Larpenteur.

UNIDENTIFIED OFFICER #2: I told him not to reach for it. I told him to get his hand out.

REYNOLDS: He had - you told him to get his ID, sir, his driver's license.

MARTIN: Another black man, Philando Castile, was shot to death in a Minneapolis suburb after he was stopped for a broken taillight. His girlfriend, Diamond Reynolds, also in the car with her 4-year-old daughter, broadcast the moments after the shooting on Facebook.

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REYNOLDS: Please, Jesus, don't tell me that he's gone. Please don't tell me that he's gone. Please, officer, don't tell me that you just did this to him. You shot four bullets into him, sir.

MARTIN: Minneapolis Governor Mark Dayton called for an investigation.

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MARK DAYTON: We're shocked and horrified by what occurred last night - a horrible, horrible tragedy, a senseless tragedy. And one that I commit as chief executive of the state of Minnesota, I will do everything in my power to see it is investigated by both the state and local authorities who have a statutory responsibility.

MARTIN: By Thursday, the deaths had sparked demonstrations in cities around the country. And then in a shocking turn of events, a gunman took aim at police guarding a march in Dallas. Five officers were killed in the attack and seven wounded, along with two civilians. Dallas Chief of Police David Brown said this at a vigil last night.

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DAVID BROWN: We're hurting, and we need this community. We need citizens to show officers that they appreciate their sacrifice.

MARTIN: After all that's happened this week, indeed, after all that's happened in recent years and confrontations between citizens and law enforcement that have resulted in deaths and injury among both, we decided to take this entire hour to talk about policing.

Almost all of our guests today are or have been directly involved in law enforcement, and we'll be talking with them about the work they do, why they do it and whether they think the system is broken. We'll talk about how they cope with the stresses of the job, and we'll be talking with folks who've looked at the latest research around policing to ask them what, if anything, should be done differently.

We start the program in Dallas where investigators say the lethal attack was carried out by a young African-American man, a former Army reservist named Micah Xavier Johnson, who told police he was angry over the deaths of black people at the hands of police. Speaking at a conference in Poland today, President Obama rejected the idea that Johnson's attack was somehow a symptom of the country's racial divide.

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BARACK OBAMA: Americans of all races and all backgrounds are rightly outraged by the inexcusable attacks on police, whether it's in Dallas or anyplace else. Transcript provided by NPR, Copyright NPR.