The gunman who killed five Dallas police officers appeared to have been planning a larger attack, Dallas Police Chief David Brown said on Sunday, after a search of shooter Micah Johnson's home revealed bomb-making materials and a journal.
Meanwhile, protests around the U.S. against the shootings of two black men by police officers continued over the weekend.
Johnson was killed by police using a remote-controlled bomb on Thursday night, after shooting 12 police officers - five fatally - at the end of a protest march in the city's downtown area. The army veteran scrawled the letters "RB" on a wall in his own blood before dying, Brown revealed, according to reports of an interview the police chief gave to CNN on Sunday.
"We're trying to figure out through looking at things in his home what those initials mean," Brown said.
The police chief said that a search of Johnson's home revealedevidence of bomb-making materials and a journal that indicated the shooter had undertaken practice detonations, Brown told CNN.
"We are convinced that this suspect had other plans and thought that what he was doing was righteous and believed that he was going to make law enforcement... and target law enforcement... and make us pay for what he sees as law enforcement's effort to punish people of color," Brown told CNN's Jake Tapper.
Brown said that police believed the deaths of Alton Sterling and Philando Castile on Tuesday and Wednesday had caused 25-year-old Johnson to "fast track" his plans for an attack on police.