As a pharmacist this guy had access to all the safe drugs he would want, so why would he take a dangerous and quite possibly lethal drug like meth?
Yeah, he did have access to all kinds of legal dope. This part of OK used to be the meth capitol of the world. Folks from every walk of life have been addicted to meth; doctors, lawyers, ditch diggers, housewives and school kids. .
The nutcase had quite a few traffic tickets. There is a good chance that whatever he was high on put him over the edge when that cop lit him up.
Maybe the cop pulled over his wife and offered her a trade. All this guy has to do is go through there well above the speed limit and he will find the cop. Cops do this every day. They are not always right, unless it is in court where for some reason his word is better than yours.
Maybe the perp was left too long in a dirty diaper, maybe his big brother peed in his wheaties, maybe the school bully tweaked his nose, maybe his mistress threw him over for a bum. Yep, it is everyone's fault except for the scumbag who murdered the cop.