Live Bait by P J Tracy

Live Bait is the second book in P.J. Tracy's bestselling Twin Cities series.
When elderly Morey Gilbert is found, lying dead in the grass by his wife, Lily, it's a tragedy, but it shouldn't have been a shock - old people die. But when she finds a bullet hole in his skull, the blood washed away by heavy rain, sadness turns to fear. It looks like an execution...
Soon a whole city is fearful as new victims are found, killed with the same cold precision. All elderly. All apparently blameless.
Detectives Gino and Magozzi, race to uncover a connection and their best hope of doing so may be Grace McBride, beautiful, damaged survivor of an earlier killing spree. And the answers, it seems, are buried in a terrible past.
Grace MacBride and Detectives Gino and Magozzi are back in P.J. Tracy's Live Bait, the follow-up to debut Want to Play? Fans of Karen Rose should be paying attention. Follow the characters' journeys in the rest of the series: Want to Play?, Dead Run, Snow Blind, Play to Kill and Two Evils.