Re: Your "nutter on a rampage" is China's "Tiananmen Square"
I heard reported on t'wireless that some of the mainstream tabloids are (or were) displaying footage on their websites.
On NZ's mainstream news media they also showed some of the footage. They showed a short clip of where the perp was getting stuff out of his car, and nothing more. The footage they showed of injured people being loaded into ambulances, or bodies in the street (perhaps pixelated or covered with a jacket) was far worse than what they showed of the gunman's own footage.
Perhaps these places showed only a limited portion of the footage. If not. then I hope there is room for them to be charged with distributing objectionable material - and as someone else said, make sure at least some of the 'C-level' types get their time behind bars.