Police believe the gunman who killed five Dallas police officers had plans for a larger attack, but acted in response to two deadly police shootings in Minnesota and Louisiana last week. Investigators are now combing through items belonging to the shooter, 25-year-old Micah Johnson, working to decipher the cryptic letters he wrote with his blood before he died.
Thursday's protest over the deadly police shootings in Louisiana and Minnesota began at a city park. Police thought the rally would remain there, but demonstrators soon began an impromptu march along Main Street, reports CBS News correspondent Manny Bojorquez. As the crowd moved, Johnson managed to stay a few blocks ahead of them in a black Chevy Tahoe before eventually finding an elevated position in buildings where he could begin his attack.
Michael Smith, Lorne Ahrens, Michael Krol, Brent Thompson and Patrick Zamarripa were all killed by the sniper fire. Police are convinced Johnson planned and practiced Thursday's deadly military-style assault. The Army veteran's so-called "move and shoot" technique puzzled responding officers.
"We got a guy with a long rifle, but we don't know where the hell he's at!" an officer was heard saying on the police scanner.
While trying to negotiate with Johnson for about two hours, police say he was laughing, singing and asking how many officers he had killed. Dallas Police Chief David Brown confirmed Johnson would only speak with a black negotiator.
"But during that talk, it didn't matter whether he was black because he was shooting at us," Brown told Jake Tapper on CNN's "State of the Union."
Unable to reach a resolution, officers armed a robot with about a pound of C-4 explosive to end the standoff.
"The suspect is deceased as a result of detonating the bomb," Brown said Friday morning during a press conference.
Police say Johnson wrote the letters "R.B." on a wall in blood during the standoff. Investigators are searching Johnson's suburban home, which he shared with his mother, hoping to decipher the initials.
Items they've recovered include a journal containing combat tactics and an arsenal two years in the making, including guns and bomb-making materials -- enough, police say, to cause devastating effects to Dallas and the surrounding area.
"We're convinced that this suspect had other plans," Brown said.
He said Johnson had been practicing explosive detonations.
"We believe that the deaths in Minnesota and the deaths in Louisiana just sparked his delusion to fast track his plans and saw the protest in Dallas as an opportunity to begin wreaking havoc on our officers," Brown said.
Police are also searching Johnson's laptop and cellphones to try and find out whether anyone may have helped him plan Thursday's attack. Johnson reportedly took hand-to-hand combat classes at a local self-defense school. Investigators have found no links between Johnson and violent extremist groups.
Protesters clashed with police in riot gear Sunday in Baton Rouge, Louisiana, speaking out against the killings of Alton Sterling and Philando Castile of Minnesota. People are leaving notes and flowers at two cruisers stationed in front of Dallas police headquarters.
Streets in downtown Dallas remain closed Monday morning as the city recovers from the tragedy.