The Aggression Scale by Steven C. Miller

5.60

When out-on-bail mob boss Bellavance discovers that $500,000 of his money is missing, he sends four hardcore hit men to send a "loud and messy" message to the suspected thieves' families. But when the killers invade the Rutledge home, they'll meet the household's emotionally disturbed young son Owen. Owen has a history of violent behavior, knows how to make lethal booby-traps and is about to teach these thugs some deadly lessons in extreme vengeance.