I think you'll find that the picture is not of *the* weapon used, but rather a stock photo used to illustrate the type of weapon, the first evening and early on the second day, when the authorities were saying "SKS". They've now gone back to saying "AK-47". Here's a photo similar to what I saw on CNN, might even be the same photo, taken from a (so called) security camera.
The sight appears too tall for an SKS, and the gas tube and receiver profiles are very AK like to my eye. Looks like it might even have a vertical foregrip by the position of his left hand.