Glavin: How 'toxic masculinity' links proponents of violence

As we all strive and struggle to sort out what rational sense might be divined from Monday’s mass murder in the vicinity of Yonge and Finch in Toronto, the likely motive that has emerged, while still necessarily a matter of speculation, involves a dark and horrible thing that the overwhelming majority of us, it seems safe to say, have never even heard of before.
What is the proper word for this thing? Is it a psychopathology? Some sort of sociopathology? Is it even possible to reduce this