The Overnights by Ian K. Smith
Ashe Cayne a ex-cop, Chicago private investigator is hired to protect a local anchor woman that has been receiving threatening letters and has an ex-stalker recently out of jail. Additionally he uses his PI skills to research assist her in her reporting of a police shooting that is much more than it seems.
Entertaining story - read in one sitting. Although this is book 3 in the series I didn't feel lost in an unknown backstory. And a high compliment to an author, I will be seeking out Ian Smith's other Ashe Cayne books to read and with plan on following this series in the future.