Chris jansing in dallas for us, thank you. Tonight theres a vigil before the president gets there at 8 00 p. M. At the Dallas City Hall blaz is a. The president , Vice President , george bush all there tomorrow in it dallas. We continue our coverage now. Kate snow picks things up. And good afternoon, what does rb mean . The shooter in dallas wrote those initials on a parking gradual in his own blood before Police Killed him. Thats just one piece of the constantly evolving puzzle of the ambush on Dallas Police officers last week. Today the Dallas Police chief outlined what we know and what we dont. Lets start with Gabe Gutierrez who has the latest. Quite a press conference from the mayor. Outline for us where were at this afternoon. Reporter good afternoon, as you mentioned a wide ranging press conference where the police chief described exactly how massive this investigation is. They are going through more than 300 witness statements, 170 hours of body cam footage and Surveillance Foot