Loanshark (Peter McCurtin Crime Chronicles Book 1‪)‬

It was one of Pete Shay’s stranger cases. He’d set out to find the killer of a small-time hood, and the trail led straight to Fat Vinny, the meanest loanshark in New York. But then Fat Vinny himself hired Shay to continue his investigation in order to prove Vinny’s innocence.
Shay knew that Vinny had never been innocent of anything in his life, but a client was a client, and Shay needed the money. He’d be up to his shoulder-holster in blood and bullets before this case was finished!