May I Have A Ride

An axe murderer is stalking the southwest side of Chicago.  All of his victims are in their teens or early twenties.  With no witnesses and no clues left behind at the murder scenes.  The police have nothing to go on except the fact that the killer works only on the weekends.

The Police devise a plan to catch the killer, but as soon as they do, he drastically changes his M.O. sending them back to square one.

How many of Chicago’s teenagers must die before this lunatic is caught?