If by "assault rifle" you mean a 9mm carbine with no ammunition, then yeah, damn, he was dangerous. I love the heaping pile of airsoft guns that they put in the picture to make it seem like he was a walking arsenal. If you'll notice, that news site also tagged a picture of a rifle scope as a "grenade".
Actually, on closer inspection, I don't see a single "firearm" in that whole pile. The 9mm carbine that they so cleverly scare us into believing is an automatic weapon (see the actual definition of "sturmgewehr" is probably a Beretta CX4 Storm...which fires pistol-caliber ammunition. That particular weapon isn't even restricted in Canada.
Not saying the kid isn't a nut. Just saying that you shouldn't buy some things (read: anything) that you hear on the news without doing some checking on your own.