NPR News:黑人老兵制造达拉斯杀警案 枪手曾计划更大规模冷血屠杀

We'll start the program today with news from Dallas, where investigators are slowly piecing together a picture of the man who killed five police officers and then injured seven other officers and two civilians. Here's Dallas Police Chief David O. Brown speaking to cnn this morning.
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DAVID BROWN: We're convinced that this suspect had other plans and thought that what he was doing was righteous and believed that he was going to target law enforcement and make us pay for what he sees as law enforcement's efforts to punish people of color.
MARTIN: NPR's Dina Temple-Raston has been following the latest in the investigation, and she's with us now. Dina, thanks so much for joining us.
DINA TEMPLE-RASTON, BYLINE: You're welcome.
MARTIN: So what are law enforcement officials learning?
TEMPLE-RASTON: Well, investigators are looking at where 25-year-old Army reservist Micah Xavier Johnson was in the days and hours leading up to the attacks. Two law enforcement officials close to the investigation tell NPR that Johnson's mother has been cooperating with authorities. And it's unclear how much time he spent at that house that they — in Mesquite, a Dallas suburb, where they were searching. It's unclear how long he actually was there and whether he had other residences they haven't discovered yet. What they did find in the house he shared with his mother were bomb-making materials, ammunition, bulletproof vests and some journal writings, which suggested that he had been contemplating violence against police for some time.
MARTIN: So, Dina, you say he was contemplating violence against the police. So is the idea that this protest just provided the opportunity that he'd been looking for?
TEMPLE-RASTON: Exactly. Law enforcement sources tell NPR that Johnson took his mother's car to the protest and that protest was all supposed to be in one place, and then demonstrators started spontaneously marching. So police were moving from block to block to protect the demonstrators from traffic, essentially blocking off streets as they went along. And they now believe that Johnson was essentially shadowing the march, driving from street to street in his mother's Tahoe SUV. And then he parked and went to higher ground where he could get a better vantage point on the police, and then he opened fire.

MARTIN: I understand that investigators found journals in his mother's house. What are they learning from those?
TEMPLE-RASTON: Well, our sources say that the journals contained a lot of diagrams and information on combat tactics. But they also contained rants that they really haven't been able to decipher yet. Investigators also have his computer, and they're scouring that for connections he might have had. I mean, they have not ruled out that he had some accomplices, or at least people who might've helped him indirectly.
For example, there was this manifesto of sorts with his picture on Instagram that was posted after the attack began. They haven't ruled out that it was something either he posted during the attack or something he had an accomplice post, or maybe this was a hoax. But now that they have his computer, that could help them figure all this out.
MARTIN: And, Dina, you know, there's also been a lot of discussion about the way the police ended the standoff. Can you tell us any more about that?
TEMPLE-RASTON: Well, the police decided to send in a robot with a pound of C-4 explosive on its mechanical arm. This is one of those robots that usually defuses a bomb as opposed to carrying one. And this is how Dallas Police Chief David O. Brown explained to cnn why they decided to do that. Let's listen to what he had to say.
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BROWN: They could not see him. And the only way to either get a sniper shot to end his trying to kill us would be to expose officers to grave danger. They presented to me a plan they put together to improvise our robot with a device to detonate within a few feet of where he was that would take him out.
TEMPLE-RASTON: You know, apparently during the two hours of negotiations with Johnson before this happened, he continued to shoot at police. And he was mocking them and taunting them. He was in a corner, apparently, so they couldn't get a clear look at him. And he said he wanted to kill more police, so they decided this was the safest way to end all this.
MARTIN: That was NPR's Dina Temple-Raston. Dina, thank you.
TEMPLE-RASTON: You're welcome.