Well, if we are supposed to believe that the killer is NOT on the SW I don't know how we could figure it out with what we know. If it turns out to be a hit but not at the behest of anyone on the SW, I certainly have no clue. JMO
First, I didn't read anything that said the killer wasn't on the "target numbers" list. Even if such was stated it doesn't mean they were not involved. Second, LE has given no other possible motives other than the ones they stated when applying for the SW's. Money & infidelity.