what does the dash cam add to this? >> reporter: it gives us an indication of what happened in the early moments of this confrontation. while police will tell you there is no such thing as a routine traffic stop. officer slaying were pulled over walter scott for having a burned out brake light. the two cars pull into a park lot. sharing asks him for his license, registration and understand card. scott says he's buying the car from a neighbor monday. he don't yet have the paperwork. while sharing is running his driver's license scott tries to get out of the car to say something to sharing. slager yells at him to get back inside the vehicle. but then scott decide to bolt