If, in fact, the guy actually was molesting the little 4 year old daughter, then the SOB got what he deserved... and that's one less "sick-O" we have to worry about.
HOWEVER... a medical examination of that little girl better "show" evidence that she had been molested (and then, the question would be... "molested by WHOM... the father, a brother, an uncle or the "perp"?) or the little girl must tell the police what the man was doing to her, etc., etc... or. unfortunately, her Dad could end up being charged with murder.
A man can't just beat another man to death, then claim the guy was molesting the man's little girl as the reason for the beating. While most of us would be in favor of seeing the perp beat to death, the law looks at it differently.