How did Paul Millander choose his victims?

In Season 2 Episode 13 - Identity Crisis, we see Paul Millander hitchhiking. He gets picked up by Pete Walker, who just happens to have an August 17th birthday? What if Pete hadn't picked him up?
Also, Grissom remarks that Millander kills in reverse chronological order; his first victim was the youngest and he kills gradually older men. How is he able to plan such a specific pattern?