Very shortly after the event, I remember one or two news reports saying the rifle was left in the car. All later reports I saw were that a rifle was used.
News organizations sometimes get information wrong when they're rushing to report on an event. That's not evidence of a lie or of a conspiracy.
“The egg hatched...” “...the egg hatched... and a hundred baby spiders came out...” (blade runner)
“Who are you?” “A friend. I'm here to prevent you from making a mistake.” “You have no idea what I'm doing here, friend.” “In specific terms, no, but I swore an oath to protect the world...” (continuum)
“It's a goal you won't understand until later. Your job is to make sure he doesn't achieve the goal.” (bsg)