I'm sure the 8chan guy knows this and wouldn't risk lying about it.
Best to wait for the facts to surface and hope the official line is presented honestly..
Trivial? Is it trivial to determine if the shooter even actually wrote it? Is it trivial to determine if HE ever posted it to Instagram or anywhere at all? Maybe someone else did.
There's nothing trivial here at all.
To determine full guilt, knowing these facts are huge. If one other person was involved, its not a lone wolf situation.