>>515733853 (OP)
It's not as simple as you think. His photos were plastered all over the internet. Without a doubt, SOMEBODY who knows him would've tipped off law enforcement, and with certainty they would know the shooter's name.
At this point you KNOW the FBI is going to kick down your door very soon. How the fuck are you going to hide your son?
And even if you know you can hide him, his life is over. He will live the rest of his days hiding in some closet, never being able to get married or have a career, and there's still always a chance he gets caught anyway.
With all this information, turning him in is probably the best outcome for him, plus you get a sweet 100K on top.