I would think if that was true then the evidence found would not point to Jr as the murderer and LE would have no evidence to arrest Heinz, Jr..Guy may have done it, but he's still innocent until proven guilty. On the other hand, how do we know he didn't cross some drug dealers who did this and he hasn't said so because they've threatened his younger brother and the rest of this family? We just don't know. I, too,find it hard to believe one person did this. But nothing's impossible, I guess.
IIRC, the police said early on that they sent a piece of evidence to the crime lab and when they got the results back is when they arrested Heinz, Jr some 8 days after the victims were killed.