Swift Justice: Book 2 in the Donny Robertson series.

Fire Captain Donny Robertson has been feuding with police constable Bill Ericson ever since Donny and his crew were unable to save Ericson's partner at a fire in an illegal drug lab. Now a string of unusual deaths leaves Donny with questions. The victims were a violent pimp, a child molester and other undesirables. No one, besides Donny is interested in asking too many questions. Everyone seems willing to turn the page, but some of the pieces of the puzzle just don't fit. Donny suspects that Ericson may have gone rogue and become 'an avenging angel'. What Donny doesn't know is that he has stumbled onto an elite vigilante squad and that he himself has now become a target.