Since my dad's stroke he's become more and more angry and verbally abusive with me and my mom. Especially my mom. We just got back from an overnight at the hospital where he was sweet as pie to all the staff, but as soon as they left, the verbal onslaught continued toward me and my mom. After asking him why, he said if I'm not nice to them they won't bring me Tylenol. So can he literally switch it on and off? He's really being abusive, or just can't help it?