Police are still investigating the hidden meaning behind the cryptic messages.

As the world reels from the Dallas ‘Black Lives Matter’ protest that saw five police officers killed and nine injured by sniper, 25 year-old Micah Xavier Johnson on Thursday night, details have begun to emerge that paint a disturbing picture of Johnson’s mental state at the time of the shooting.

In an interview on CNN this weekend, Dallas police chief David Brown said messages scrawled in blood were discovered throughout the building where Johnson was carrying out the attacks.

“We are trying to decipher [the messages], but he wrote the letters ‘RB’… We’re trying to figure out through looking at things in his home what those initials mean, but we haven’t determined that yet.”

It’s thought that the sniper was wounded while making his way up the building’s stairwell, where police negotiated with him for several hours before eventually letting off an explosive that killed the 25 year-old.

Johnson was an army veteran (Facebook).

Johnson during his time serving in the US military. (Facebook).

So far it’s known that the shooter had no criminal history prior to the attacks and had served time in the army during which he undertook a stint in Afghanistan.

A journal found in his home indicated a history of mental illness.

“I think that this killer had some delusions, there was quite a bit of rambling in the journal that’s hard to decipher,” Brown told CNN.

Bomb-making equipment and ballistic vests were also discovered in Johnson’s home, along with several riffles and ammunition, though investigators weren’t able to find anything linking the attacker to the Black Lives Matter movement where the police-targeted shootings took place.

Images via Facebook.com.