Sounds like a job for CSI... Is the residue on Juan's hands from shotgun powder, or from handgun ammo, or both...
Well, none of us knows for sure if this was murder or suicide, but a few questions by law enforcement do seem appropriate. Initially, suicide seemed so believable; it seemed exactly like what we'd expect from this man. And maybe I'm just an odd duck, but had my father killed himself with a pistol the first thing I'd have done would not have been go outside and pop off three blasts from my shotgun. It just seems way too convenient to explain powder residue on Juan's hands.
Sounds like he hated the scarf.