I think he was under the influence of a cocktail of the drugs cannabis and cocaine,which he had tested on rats to steel himself for the task in hand. We know Jeremy liked to mix drugs from his deglutation of alcohol and valium tablets on the morning of his parents' funeral.
Steve,,it's not unusual for anyone to be given valium after a tragedy,,,certainly one as big as this one. Jeremy may have had difficulty " keeping himself together " after such a loss,,,and I don't imagine that he took other drugs with his prescription ones. At the funeral,,,he looked,,to me,,that he was holding a lot of emotion in.