Which doesn't seem to be wrong? At least from the linked document, he went to prison for non-violent drug crimes, unless I misunderstand what the document says?
Him claiming he's in prison for non-violent crimes (like he's your local herb dealer) takes gumption...Authorities linked his Carfentanil escapades to several deaths.
Indirectly causing a death doesn't make a crime violent. A doctor guilty of fatal negligence isn't a violent criminal either.