True. If anything, most of the interviews with acquaintances paint the dead man as "simple," perhaps even Gumpian. That could be revisionist history, spoken by people who grieve, but if there had been violence in his past, we would likely have heard about it by now.
My fearless prediction: It's an inside job, but the delivery man wasn't in the loop. He was just used, then discarded.
Wouldn't an "insider" know when the bank vault would be open (i.e. 3PM rather than 2:20)?!