 Zapruder initially decided to film the motorcade from the window of his office but later decided to film from Dealey Plaza as the angle was better.He chose a concrete abutment which extends from a retaining wall that was part of the John Neely Bryan concrete pergola on the grassy knoll north of Elm Street, in Dealey Plaza.Sitzman offered to join Zapruder as he suffered from vertigo and was apprehensive about standing on the abutment unassisted.