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.
Imagine a pathologically idealistic, anti-religious, culturally-relativistic, iconoclastic, socially-irreverent, sociologically-progressive signature line here. Or don't.