People who chronically disobey laws WRT driving lose their license, which is also supposed to remove the privilege. We all see how well that works.
Cars aren't supposed to be a weapon, so there's really no reason to fear the government taking them all away. An argument by people who don't like ANY government or as little as possible don't want the government to know where the guns are- kind of a moot point since an application is filled out and sent to the FBI along with the ability to track addresses when people move, but, well....
Questions need to be asked- it WILL stop some of the killing.
If you shoot someone while trying to stop a shooter, you WILL be sued, but there will also be an investigation as to whether they were shot intentionally, unintentionally or carelessly- the second could be a bullet passing through/grazing the shooter or ricocheting, the latter could be from squeezing a round off while running, waving the gun hand, or just not aiming. Expect a civil suit.
For the last question, the same would result, but that's the reason it's best that people pay attention and keep their eyes moving. In a large area or building, that becomes harder to manage- however, the sound of a handgun is so different from that of a rifle that it would be safer to shoot at someone with a rifle, if one is being used. Gun owners should leave theirs at home if they haven't been trained in tactical shooting.
I believe people should be allowed to protect themselves, but they need to be sensible about it. Hard to be if the adrenaline is rushing.