Hi Chow,
The 7.62x39 round fired by the Ak-47 actually makes a good deer round. Diameterwise its equivalent to a .311 caliber, which is just a shade bigger than the .308 which is common in the .30-06, .308, and .30-30 rounds which are arguably the most popular caliber for North American Deer.
As for the Ak-47, they're perfect firearms for the outdoors, they operate in the worst of conditions, and rarely jam. They are a shade less accurate than your typical hunting rifle due to the shorter stock, and often canted sights... but with enough practice it can shoot quite nicely. This article (I read it as well) was incorrect in its terminology... the Ak-47 refers to the fully automatic version of the rifle, while the AKM is the semiautomatic "civilian" version. I can almost guarantee he wasn't using the fully automatic version. There are actually a lot of folks across the country that use their AKM's for hunting. They're easy to get your hands on and are pretty cheap to own and shoot. They're actually legal to hunt with in Oregon provided you use a 5 round magazine with it.
With that said... while it has appreciably similar stopping power as a .30-30 round, the safety and accuracy is not ideal on the AKM and its variants. It's a selector switch on the right side of the rifle, and can easily be tripped downward putting the rifle into fire, and resulting in the really unfortunate accident in the article, but if you're comfortable with the rifle, and extremely careful, then its not a safety and accuracy is not a major problem.
Biggest issue with this situation was muzzle control. I don't want to armchair quarterback this one, but if his muzzle had been controlled, the accidental discharge would not have hit anyone.
Hope that helps!
Bulk