I use the same reasoning out here in Kali whenever a gross murder is committed or really whacked out crime of violence like this one. My poor wife and DIL don't even call me a red necked racist any more when I use the same reasoning and deduction/elimination that you did.
My oldest son learned not to bet me on situations like this. I took him for a $100 bet right after he was graduated from college. He is still about $85,000 ahead on the deal with the Grampa Dave scholarship funding program for he and his brother. He's a smart kid and never bets his old man any more.