Although I have no knowledge of how to change an AK to select fire (there, I satisfied the ATF conspiracy ruling), rumor has it that it isn't that hard if one has the proper parts, or the plans and a decent CNC machine. I doubt the rifle was "professionally converted."
I have seen some of these rifles (the original AK import) that had dimples on the lower section for drilling the holes for installing the select fire parts. There are also templates available online so it would be hard to tell if the job was “professional” or not. I am sure that the shooter wasn’t interested in breaking that particular law when he was going to break the big one anyway.
yeah...professional, right...i bet he looked it up on the internet and borrowed his buddy’s dremel tool.