Keeping on the Alphabetical regime, and catching up with an overdue review book - The Third Rail by Michael Harvey is the book that stuck out in the H pile.
From the Blurb:
A woman is shot as she waits for her train to work. An hour later, a second woman is gunned down as she rides an elevated train through the Loop. Two hours after that, a church becomes the target of a chemical-weapons attack. The city of Chicago is under siege.
Opening Lines:
Robles had been on the platform for less than twenty seconds. He leaned against the railing and peered through layered curtains of snow, at the stone faces of apartment buildings crowding close to Chicago's elevated tracks.
A woman is shot as she waits for her train to work. An hour later, a second woman is gunned down as she rides an elevated train through the Loop. Two hours after that, a church becomes the target of a chemical weapons attack. The city of Chicago is under siege.