The motivation of Jo Cox's shooter has to be one of hatred and trying to assert control over the vote to separate Britain from the European Union. Cox was a vocal and well known supporter to keep Britain in the EU. While he was attacking Cox, the shooter shouted political slogans that professed his support to separate Britain from the EU. His attack was his political statement.
Jo Cox's shooter shouted the words "For Britain!" when he stabbed her. He had a long history of association with white nationalists online. Jo Cox was known for her support of refugees seeking asylum in Britain. Many people from racist groups did not agree. Her assassination was a reaction to that.
It would appear that any time somebody shoots up a place or kills somebody that it is some sort of a statement. This can only be determined by the motives of the shooter and what they perceive as political. It would seem that people would use politics as an excuse for senseless violence.
Of course, Joe Cox's shooter was making a political statement. That is what radical Islamic fundamentalism and its actions is all about. Unless and until this radical ideology is dealt with we can expect to see bees, and many other forms of, shootings and terrorist acts for the foreseeable future.