If this guys is the perp, he could have based his selection of victims based upon the fact that they were probably in "Condition White" as evidenced by the fact that they were running through an isolated section of the park while wearing headphones, and probably oblivous to any potential threats. I run through fairly deserted parks (and questionable neighborhoods) while wearing an MP3 player with headphones, but I always keep the volume relatively low, and pay close attention to my surroundings - And, I'm a 225 lb guy with martial arts training, not a 110 lb woman. Women running alone should avoid that kind of danger area, especially when they are tuned out wearing headphones.
Dr. James Fixx, the guru of the jogging craze, died at age 42 - while jogging!