dad thinks my mom & sister (primary caretakers) are trying to kill him

Hey all - my Dad is 83 and in the later stages of Lewy Body Dementia. His paranoia and delusions and hallucinations, which he's had for a while now, have just turned so dark and scary. He thinks my mom and sister, his primary caretakers, are trying to kill him. He think my mom murdered my 10 year-old son. His reactions to all of this are aggressive, sometimes physically aggressive. I know these thoughts are inevitable, even with the meds, but does anyone have any idea how we can turn the tide on how violent they are? He always loved CNN and my Mom has let him watch it for years to past the time, so I have tried to tell her to have him watch lighter fare (he barely sits for TV anyway these days). Does anyone else have any ideas?