I just don't see what makes people do something like this - in cold blood.
The ONLY good thing about it, was he eventually felt remorse and guilt - after having gotten away with murder (literally) - he confessed.
I do believe he deserves a meeting with his maker - because if I had heard that confession, and it was one of my little girls, it would take the entire Houston Police Department to keep me from arranging that meeting.
It is clear he felt guilt; but is remorse necessarily an aspect of 'feeling guilty'? I don't know; even as he 'repents' he seems beyond the 'feeling tones' of genuine remorse - and in 'pogram mode' - or so it seems to me, just in a quick read. . .
Could be that he is a border-line sociopath - rather than full-blown, that is - but whatever his psychological state, this movie reached just enough of him for a confession. . .