Whoever was the culprit...I think he had to know Hatfield in some capacity...there are several indicators to point toward Hatfield...and I think that was done intentional...to take the FBI off in the wrong direction for months, if not years.
It's Hatfill. According to Berry's father they do know one another. This is no assumption of Hatfill's guilt, it's just that this is a rather small group and they ALL know each other in one way or another.