Yes, but JMO, but I'm pretty confident LE would have already investigated this possibility by this point.
And perhaps found alibis that did not hold up. Yes, I think it's possible out of those 50-60 POI someone could have past connections to the plant right down the road.
As I read the description of the desensitization that occurs with that work and couple it with the knowledge of people with criminal backgrounds employed there my mind flashed to the guy a few days ago who made the comment on the news page, (Kokomo maybe?) his user name was thedeerhunter. His comment was too graphic and hopefully has been deleted by the news outlet and the lead followed up by LE.