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By Hasani Gittens

Micah Johnson, the man who shot 12 police officers, killing five of them, in Dallas may have had grandiose plans of mayhem, the police chief said Sunday.

The suspect had enough explosives to do damage "throughout the north Texas area" — and left a final message written in his own blood mysteriously saying "RB."

Micah Xavier Johnson, suspect who was killed after a standoff in the ambush of 12 Dallas police officers on Friday.via Facebook

Dallas Police Chief David Brown on Sunday said that a search of Johnson's home in Mesquite, Texas, led them to believe "based on evidence of bomb making materials and a journal that this suspect had been practicing explosive detonations and the materials were such that it was large enough to have devastating effects throughout our city and our north Texas area."

The chief made the comments Sunday morning in an interview with CNN's Jake Tapper. Johnson's writing indicated that he felt he was doing a good thing.

"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 said.

Related: Suspect in Dallas Sniper Attacks Believed to Be Lone Gunman

The chief added that the killer "obviously had some delusion" and "there was quite a bit of rambling in the journal that’s hard to decipher."

"At the scene where he was killed he wrote some lettering in blood on the walls, which leads us to believe he was wounded up the stairwell on the second floor of the El Centro building where we detonated the device to end the stand off there was more lettering written in his own blood. We are trying to decipher that but he wrote the letters 'RB.'"

Brown said that investigators are still trying to determine what those letters and other references in his journal and home might mean.

The police chief also said that Johnson was laughing and even singing during the standoff.

"We had negotiated with him for about two hours, and he just basically lied to us — playing games, laughing at us, singing, asking how many (officers) did he get and that he wanted to kill some more and that there were bombs there," Brown said, "so there was no progress on the negotiation."

"I began to feel that it was only at a split second he would charge us and take out many more before we could kill him," he added.

"Without our actions, he would've hurt more officers," said Brown, who defended the use of a bomb-toting robot to kill the suspect. "We had no choice in my mind but to use all tools necessary and it was about a pound of C-4 to end the standoff."