I either missed this, or is has been added to the article:
Audio recording from Pearson's air traffic control tower shows that Delta Air Lines Flight 4819 was cleared to land shortly after 2 p.m. and that the tower warned the pilots of a possible air flow "bump" in the glide path from an aircraft in front of it, according to a report from The Canadian Press.
So wake turbulence could be a factor.
I'm unfortunately not free tomorrow, but Apocalyptica is pretty great. Anyone who has the opportunity to see them should take it.