He asked his assistant for a big one( dose) He got it.
I am sticking with suicide. He was an alcoholic and drug addict, who had money, but couldn't use it to buy drugs or booze.
He abused Ketamine, and I think he realized his career was over and as a celebrity who was a sobriety advocate, he had to watch his behavior.
Not everyone is happy being sober. Maybe he got sick of life and wanted to get back at those, who took advantage of him.
He may not have wanted to die with pills and booze.( cliché) or looked bad, by slipping off the wagon.
Besides he was depressed, and maybe he just wanted to die. He was getting Ketamine infusions.