Whomever Peter McCurtin was, he surely was a crafty devil, churning out Assassin novels for Dell and Marksman books for Belmont/Tower, even though obviously both characters are exactly the same. Both antiheroes even have the same origin: New Orleans-based gun dealers who seek revenge against the Mafia after their families are murdered. I have no idea who McCurtin pulled it off, but my hat is off.
The second Assassin novel, NEW ORLEANS HOLOCAUST (Dell, 1973), sends Robert Briganti back to his hometown to find the brother of one of the hoods that killed his family prior to the first book. There isn't really any more to the plot than that. In fact, that story's payoff pales a bit next to some of the side jobs Briganti takes on before and after he arrives in New Orleans.
A nasty setpiece finds the Assassin on the prowl for two gay Mafia hitmen who tortured and killed a young stripper with whom he knew as a kid growing up in the carnival business. McCurtin briefly introduces a temporary new partner for Briganti: a retired corrupt police detective who helps the Assassin prowl the underworld for one of the fiends and dies heroically in an absurdly public shootout.
Little in the way of characterization or anything exuding realism, but blunt and entertaining. Briganti's gimmick of recording his exploits on cassette tape and sending them to the FBI is an interesting one.