I just found this thread and haven't read everything yet, so I apologize if I am bringing up something that has been discussed.
According to the family website, Terry was obviously an active and long-standing member of AA/NA. Could he have met his murderer(s) at meetings? I attend NA and due to the nature of the beast of addiction, going to meetings can put you in contact with people "unsavory" pasts - certainly people with criminal pasts often involving drugs and violence.
Could Terry have reached out to a suffering alcoholic or addict and had it turn bad? I just wonder if this is an angle has been explored. I will continue to read the thread, but wanted to throw out this thought.
I do not intend to tiptoe through life only to arrive safely at death!