Dealing With Prison - From Mum

My son is in prison for a violent offence and will not be home for a very good while.
Up until two years ago, I used to call anyone associated with a criminal, scum. Not nice I know but I wasn't brought up to break the law and I followed the law through family traits. I brought up my two sons with exactly the same principals but two years ago my world fell apart. 
My son committed an awful crime and I have no idea whatsoever triggered him to do this.
He had done well at school and uni, and got some brilliant qualifications. He is clever, polite and generally a good lad. He didn't give me much trouble when he was a teen and neither did his brother. I thought I was lucky compared to some teens these days.
I had always had a very open relationship with my sons and they always confided in me about girlfriends and problems.
Their problems weren't major ones by the way, they were just the odd thing in general. None of them were bullied nor did they take any illegal substances. 
So what went wrong because I do not know. All I do know is that my world has been shattered. It goes to show that anyone and any walks of life can end up in prison. I will have to deal with it, I have little choice.