SKS is made with a 10 round fixed box magazine. It has no pistol grip or detachable mag which makes it an 'assault rifle'.
There are conversions to make it take AK mags,but they are rare, difficult to modify correctly, and not that well thought of.
If he did indeed use an SKS, it was 99% likely to be the standard 10 round fixed magazine variety.
So if an M1 was legal during AWB the SKS was also legal?
My SKS is a Yugo model with flash supressor and bayonett. The magazine is fixed 10 round that uses stripper clips and there is no pistol grip, so It only has two of the dreaded three physical characteristics that would classify it as an "assault weapon".
It's just a semi auto rifle.