Triple Cross (Alex Cross #30) by James Patterson

They strike under cover of darkness, trigger no alarms, and leave no evidence behind.

Detective Alex Cross is hunting a killer who targets families around Washington, DC. But Cross isn't the only one investigating.

A charismatic true-crime author has spotted patterns in the actions of 'The Family Man' that others have missed.

Its up to Cross to determine whether the writer's theories are fact or fiction.