Why Are Nolan Wells' Witnesses Too Scared To Talk?

Somebody on that boat trip knows more than they're saying about what happened to Nolan Wells, and some of them are reportedly too scared to say it. 
Nolan was eighteen, a wide receiver at Southwest Mississippi Community College from Ocean Springs, Mississippi. On the Fourth of July he went out to Horn Island, an uninhabited barrier island roughly ten miles off the Mississippi coast, with a group of friends. No buildings, no fresh water, no service, just boats and coolers until the sun goes down and everyone heads for the mainland. His friends made it back. He didn't.