Amid Deepening Investigation, A Clearer Picture Of Dallas Shooter Emerges

The man who fatally shot five police officers in Dallas may have had plans for a wider attack, the city's police chief said Sunday. Dallas Police Chief David Brown provided new details about the tense two-hour standoff that police had with the gunman before he was killed.

"We're convinced that this suspect had other plans," Brown told CNN, adding that the shooter "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."

Investigators are looking at where former Army reservist Micah Xavier Johnson, 25, was in the days and hours leading up to the attacks. According to two law enforcement officials close to the investigation, Johnson's mother has been cooperating with authorities to help them piece together what happened before the attacks.

Officials have searched a home Johnson shared with his mother in Mesquite, Texas, just outside of Dallas, but they tell NPR it is unclear how much time Johnson actually spent at that residence and whether he may have other apartments in the area that they haven't yet discovered.

In the search of the house in Mesquite, officials say they found bomb-making materials, detonators, ammunition, bulletproof vests and some journal writings, which suggest Johnson had been contemplating violence against police for some time. The materials suggest that the protest on Thursday night just happened to provide him with an opportunity to carry those plans out.

Law enforcement sources tell NPR that Johnson drove his mother's car to the protest. Police and demonstrators had originally agreed that the protest would be static, in one place, but then people spontaneously started marching. This set police scrambling ahead of them to block traffic as they went along.

Investigators say they now believe that Johnson essentially shadowed the march, driving from street to street, and then parked the car and went to higher ground where he could get a better vantage point on police. Once he was in position, he opened fire.

Investigators tell NPR they also are starting to look at Johnson's online history, and have mirrored the hard drive on his computer to see what they might discover there. They haven't ruled out that he had accomplices, or at least people who might have helped him indirectly. There was, for example, a manifesto of sorts with his picture on Instagram that was posted after the attack began. Officials haven't yet ruled out that it was something either he posted during the attack or had instructed an accomplice to post should he be killed.

Now that officials have his computer, that could shed some light on that part of the investigation.