There was a tweet during the time the story was developing that was a repost of an email sent to the community by hte school touting their new security plan - and it said the school doors would be locked at @0930 every school day. He came in just before that...

The reason folk - other than folk like us - are not discussing the motive, is because it's all speculation unless the perp published a manifesto, left a note, told a friend, etc... None of that has come out, so we can say whatever we want, but until we know it's all just stream of consciousness spreculation... Not that that's bad. But it is what it is.

MCB