Driving alone occupies one's full attention. Handling a firearm occupies one's full attention. One needs to choose which.
And I never transfer a firearm from my control unless it is to that of a person in whom I know I can fully trust it with and to handle it according to protocol.
William failed in both areas.
Nor do I. I have to find a safe place to park where I can re-arm without alarming the public.
I doubt the people in the article were in motion either. I bet a conversation turned to the similarity of the two guns when the driver, safely parked, was re-arming. Why he would hand anybody a loaded gun under such circumstances is beyond me.
I've taught several people about gun handling. They don't get to touch a gun until they can recite from memory the four safety rules. They never see ammunition and a gun in the same room. Ammo isn't near the gun until we get to the firing range.