Not only did he victimize someone outside of his family, Patrick had the audacity to act on his deviant behavior in a home where the parents and seven other children were sleeping. Very risky. Very arrogant.
Patrick talks in his evaluation about "the thrill of the hunt." Scary.
In hindsight, that makes sense to me now, in a sick sort of way. Remember that Jim Cameron and Dave Barrueto already knew Patrick had done much more than kiss our child. They didn't need to read the evaluation to find that information out.