Chat with us in Facebook Messenger. Find out what's happening in the world as it unfolds.

DALLAS, TX - JULY 08:  Dallas Police Chief David Brown pauses at a prayer vigil following the deaths of five police officers last night during a Black Live Matter march on July 8, 2016 in Dallas, Texas. Five police officers were killed and seven others were injured  in a coordinated ambush at a anti-police brutality demonstration in Dallas. Investigators are saying the suspect is 25-year-old Micah Xavier Johnson of Mesquite, Texas. This is the deadliest incident for U.S. law enforcement since September 11.  (Photo by Spencer Platt/Getty Images)
DALLAS, TX - JULY 08:  Dallas Police Chief David Brown pauses at a prayer vigil following the deaths of five police officers last night during a Black Live Matter march on July 8, 2016 in Dallas, Texas. Five police officers were killed and seven others were injured  in a coordinated ambush at a anti-police brutality demonstration in Dallas. Investigators are saying the suspect is 25-year-old Micah Xavier Johnson of Mesquite, Texas. This is the deadliest incident for U.S. law enforcement since September 11.  (Photo by Spencer Platt/Getty Images)

    JUST WATCHED

    Dallas gunman wrote 'RB' in his own blood

MUST WATCH

Dallas gunman wrote 'RB' in his own blood

In an exclusive interview, Dallas Police Chief David Brown explains to Jake Tapper how the killer wrote "RB" on a wall in his own blood.

Dallas gunman wrote 'RB' in his own blood

In an exclusive interview, Dallas Police Chief David Brown explains to Jake Tapper how the killer wrote "RB" on a wall in his own blood.