Reading those old news articles, it seems possible that the girls might have been hitch-hiking, or accepted a ride from someone they did not know well, imo.
Maybe they were followed by someone on their travels around the city, maybe the perp/s were eavesdropping and heard about the birthday party and other destinations for the evening?
Maybe they were followed by someone on their travels around the city, maybe the perp/s were eavesdropping and heard about the birthday party and other destinations for the evening?