I really want to know if anything besides money received from the bank was stolen. As I recall early on it was reported that whoever was involved also took banking papers. If only banking stuff was taken - bank account info and money from the bank account - that could have been the motive of whoever was in charge where they were getting revenge on the S family based on some perceived financial slight and the torture may have been directed by the planner or could have been those executing it deciding to do that on there own. I know of one person who could be interested on the financial side where they felt slighted by the S family, but that was many years ago before PS was even born, but I'm sure there's many other people out there who may feel like they've been financially slighted by the S family if for no other reason than because they dealt with so many people that a few of them would inevitably be nuts. If purely BoA money and paperwork was targeted, it would seem like whoever did this really felt like the money in that account belonged to them, like some statement was being made in what was not stolen - the closest analogy I can think of is from Treasure of the Sierra Madre where Dobbs and Curtin beat McCormick senseless and they only take the exact amount they were owed even though they could have taken thousands more where they made a statement in not taking any more than they did by throwing the leftover money at him once they agreed upon the exact amount they were due.
I haven't seen anything reported about anyone taking banking papers.