James V. Viscosi 
Night Watchman [EPUB ebook] 

Nate Watson is a cop in a bad section of Island City. Responding to a call from a frightened old woman, Nate and his partner encounter a group of young men playing at dark magic on the decrepit rooftops of the slums.

Except they’re not playing.

Overpowered by the boys’ mysterious abilities, Nate’s partner meets his death at the bottom of a ventilation shaft. He’s the lucky one. The boys drag Nate into a circle of candles and saw him open from neck to waist, playing with what they find inside. When he dies they lose interest, snuff the candles, and depart. The night cools. The crows come to feed on the corpse. But then the candles flare back into life, and the birds take frightened flight, and Nate Watson returns … with a vengeance.