From what I've heard? That 'something they do inside of prison' usually is 'be a pedo.' Fellow prisoners don't exactly wanna hear tales of their pedo fellow prisoner's sexual escapades, and they have a tendency to just not shut the fuck up. But. Well. There's one thing that (usually) works...
The 'raped an elderly relative' is going to be definitely part of what ensures the other inmates are going to be seeing as part of the 'freakish demeanor,' and if he's considered enough of a sick freak by everybody? The guards might not ask too many questions about mysterious injuries, blood puddles, gore...'mysterious' disappearances...
I know of somebody who did go that way. Turns out even pedos can have standards...