What would you do if your best friend was killed?

Let's say you have a best friend named Shawn. ( 35) Shawn was a fun dude but he has a bit of a temper. He had a wife and a stepson that you knew he hit a couple of times but that's it.

One day you completely stop hearing from Shawn. The police are doing a search for him because he's gone missing. When you go over to the house, His stepson ( 16) is a little awkward, extremely nervous and says I don't know where Shawn is, I don't know what you are talking about and quickly shut the door. - what would you do?