Not an AR15, NOT an SKS, it is an AK-47 variant called a Vepr.
I seriously considered purchasing a VEPR in 308 Win years ago--a fine rifle that is a cut above most AKs. Whatever it is, the receiver is stamped, not milled.
It is an AK-74 (5.45x39mm). One can tell from the lesser curvature and length of the magazine. AK-47 mags are longer and have a pronounced curvature.
In the photo of the dead guy, there’s a white strap of some kind and on it you can make out “62 MADE” which would work with 7.62. Or not.
No it’s not a Vepr.
He could not mount that stock with the Vepr trunion.