Makes it sound like he was a Bible Thumper.
Prayers for the family. Their heads might have been screwed on right, but sadly their son choose to reject the truth (granted mental illness may also been at play - which can effect the 'choosing' part. But illness or not, their son chose to go the way of evil).
It happens. Eli's sons Hophni and Phinehas were evil. Samuel's sons Joel and Abhi were also apparently no goodniks. And Manasseh, the son of the Godly king Hezekiah, was a vile rejecter of God. But God loved Manasseh, nonetheless, and beat the crap out of him in his old age so he finally walked humbly before The Lord before he died.
We raise our children as best we can, and point them to The Lord, and pray for them. Sad when one is snatched away.