[Avodah] Mourning an Abusive Parent

[Cantor Wolberg via Avodah]

Since the topic of Agunah indicated that she still would have to sit shiva for him
even if he were a menuval. So I have the following question:  If an adult child
murders his parents, is he mechuyav to sit shiva for them? I know that sounds
ridiculous but since it can happen, what is the halacha?
My second question is: Can you learn Torah from a known pedophile?
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