That would be a slightly modified Saiga. The forward hand grip is what gives it away. The folding rear stock is not oem, probably swapped out for ease of concealment under a jacket. The scope and the scope base are not oem Saiga.
Saiga platform weapons come in many calibers/gauges.
5.45, 5.56/.223, 308, .410, .20, .12 gauge, and of course the 7.62x39 round.
In other words a “fancy” but well built AK-47 variant.
Saiga AK-74
Of course, the pictured rifle may not be the one used but the one planted before the picture was “leaked” by the FBI Evidence Destruction and Coverup Teams. Sure looks very undamaged after being hit with a pound of C4 and a firefight.
Additionally, watching the news broadcasts of the FBI teams recovering an “arsenal of weapons” from the shooters house appeared to be a couple of brown bags. If there had been an arsenal 15 - 25 weapons and 50,000 to 100,000 rounds of ammo, I’m sure that they would have been prominently displaced for the public’s awe.
The whole single “lone wolf” shooter stinks of a gov’t false flag act.
At this point I would have to start asking who said it was an SKS in the first place.