After the shooting of the robber with the toy gun the bullet is removed from the wounded man at the scene by the ambulance attendant shortly after having arrived. In 1963 an ambulance attendant did not perform that kind of procedure at the scene. Even trained paramedics of today would leave the removal of a bullet to a doctor in a hospital.
Stanley, impersonating an NYPD officer, draws his revolver and shoots a robber who was brandishing a toy gun. Later the slug removed from the robber is identified as a .22 caliber slug. However when Stanley is shown pointing his revolver directly at the camera the chambers in the cylinder are clearly visible and are clearly of a caliber much larger than a .22. They are more the size that would accommodate a .38 special round which is much bigger in diameter than that of a .22 cartridge.