Anyone who is half awake can see there was a field of fire and all those people who ran to the grassy knoll knew one of the killers werwas there.
No, they don`t “know” it.. they were chasing a sound that very likely was an echo. Eyewitnesses saw Oswald in the 6th floor window. And oh, by the way.. can anyone explain the “curtain rods” Oswald told Wes Frazier he was carrying into the TSBD?