Happy Hour Murders

Salvatore isn't an author as he claims. In fact, Salvatore Cabella isn't his real name.
A successful assassin for the past twenty-five years, he was trying to retire when his girlfriend on St Kitts was kidnapped. Unless he whacks someone in the witness protection program before they can testify, she'll be killed.
Following instructions, he moves into an active adult retirement community in Glenwood, Arizona where the smiling residents and their bizarre lifestyle affect him. He discovers he longs to enjoy life as they do.
Walking home from Happy Hour, he discovers his latest neighbors and a US Marshall have been slaughtered. The local police team up with the US Marshall Service to hunt the killer(s) down.
With everything at stake, will he save his girlfriend and retire, or will his friendlier self get him killed?