The big difference is that you're not seeing that there's a person in front of you on the Internet whereas you are necessarily confronted with people's reactions and emotions in speech-based forms of contact, irrespective of whether you register them.
I looked at websites of The Daily Mail, The Guardian and the BBC.
The former two are both reporting the 'Britain First' shout, naming different witnesses.
http://www.dailymail.co.uk/news/article-3644847/Woman-MP-Jo-Cox-stabbed-shot-twice-man-makeshift-gun.html...
I'm basing my comments on:
-- the fact that an MP is in a critical condition as a result of one or both of being shot and stabbed
-- several witnesses heard the perpetrator shout Britain First before committing the act
Do let us know when you deem it appropriate to arrive at a conclusion.