The crowd in Dealey Plaza are shown panicking and diving to the ground when the gunshot sounds, but in reality most people who were present reported that it sounded like a car exhaust backfiring and nobody reacted in the manner shown.
Agent Livingston pulls his weapon when Dr. Fitzgerald picks up the camera, and Dr. Fitzgerald tells him it is not a weapon. The camera had already been examined so they would know it isn't a weapon.