Just realized your link is Sorcha Faal’s page.
Might be a grain of truth in that report but most is likely false.
Well, I have no idea who Sorcha Faal is so I’ll defer to you.
http://heavy.com/news/2015/10/chris-mercer-harper-umpqua-college-shooting-roseburg-oregon-isis-islamic-state-news-videos-pictures-photos-attack-influence-terrorism/
http://www.jihadwatch.org/2015/10/islamic-state-claims-chris-harper-mercer-mass-murder