Not phased by dad leaving?

My dad has been there for me for my whole up to now 16 years of my life. He's always said he's loved me, he's never really abused me, but I feel that I never really have been that close to him. Just two days ago, my parents got into an awful fight because my dad hit my four year old niece on the arm with a belt because she wouldn't eat her cereal. Two days later, the mark is still there and a huge bruise is forming. His whole family is saying they're coming to "get" her, and one of them is supposedly coming to get my niece. The thing is, I only feel bitterness towards my dad. I'm not really sad about him leaving. I don't know if this is normal...I mean, I love my dad, but he needs help. He's on nearly 30 different pills a day, and he IS addicted. He's at the Jail hospital in acute care right now, so he'll get out in a few days. Is it okay that I feel no sadness in him leaving?