Hmmm....why did JB have to get the rats stoned and "test his will" by allegedly strangling them? Seems an awful lot of bother to go to,and as Susan pointed out,a sheer waste of weed 
And how would that prepare him for murdering his family with a rifle? 
Tyler,it may answer some of your questions to learn that the story came courtesy of Steve and whilst not for ONE moment am I suggesting that he made it up, I won't vouch, with the same certainty, for the integrity of the publication which first insinuated the story.
There are several points, regarding this colourful tale, which IMHO, must be raised. Firstly, how did he catch the rats? My father, a champion ratcatcher when he was 9yrs old, grabbed them by the tail and dispatched them against a wall. Let us suppose that Jeremy, probably NOT a champion ratcatcher, manages to grab a tail. What next? Does he put dope on Ratty's favourite food and wait for him/her to become hungry? How does he know how much to administer in order that Ratty doesn't die BEFORE strangulation which brings me to my next point. I am reliably informed that it isn't possible to strangle a rat. Whether this is because of its physiological make up, or from fear, that having once let go of its tail, it could inflict a nasty bite, I know not.
All in all, it seems like a great deal of time, trouble and good dope wasted on an exercise to prepare himself for shooting his family.