The Injustice of Valor. Valorie Dawes Thrillers, #6

When the cops and courts fail, The Redeemer exacts his own form of justice. When the bodies of freed sex offenders turn up with increasing regularity in western Connecticut, the Clayton Police Department responds with a disinterested yawn. Second-year cop Val Dawes doesn't share the department's apparent indifference to the trend of vigilante justice. But her warnings fall on deaf ears, especially after her jealous rivals in the department get her suspended on a bogus assault charge.
Then her best friend in the department, a trans woman named Shelby, goes missing under suspicious circumstances. Can Val find her friend before she, too, falls victim to a deranged vigilante?