Some people are "injustice collectors." Those who store up anger at any and all wrongs they believe have been done to them..Such a person could be angry enough to kill. A tenant, a receiver of some service from RJR, a former or current employee, a relative who feels mistreated or left out of the "pie" so to speak.
On the other hand, anger may not have played into the motive at all. Someone may have been interrupted in a burglary, there may be fraud going on that was discovered recently, a love interest may have taken out the one person in their way..this would imply as I have hypothesized before that only 1 persons targeted and the others were collateral damage.
I have no knowledge if any one of these scenarios is more likely than the others, but at this point in time, I consider all of them possibilities. JMO