He also made the first attack in mid-May, at about the same time (May 16) the D.C. police searched Rock Creek Park for the first time, according to the time-line link posted above.
So, not only does this guy keep attacking women in the same area where his supposed first victim's body lies, but he does it around the same time the D.C. police start searching the park -- anyone with a TV would know about the investigation, and everyone's attention is focused on that area of the park. The attack cases prominently feature Walkmans, it is noted that he wasn't attacking to steal the Walkmans, and one is conveniently found near Levy's body. This smells.
He was probably very much on the lookout for women wearing walkmans, however, because they are easier to sneak up on.