Advice on my book?

Well, it’s mostly a question. But hi, everyone. I have written a book where two male detectives in their mid 20s are working in the NYPD, and they both are to investigate and solve a case where this “main” suspect would hire men who are a part of his gang who murder their wives and children for money. I have my two main characters who are detectives, and I cannot figure out what kind of unit or division they would work in to solve a case involving a group of men who murder their wives and their children for money. I was thinking maybe a gang unit, but I look it up on Google and it doesn’t talk about what exactly what kind of crime it is for a main suspect who would hire men to join his gang and use them to kill their wives and their children. I was thinking maybe I could make up a make believe division or unit. If anyone is willing to help, I will really appreciate it. I know some of you aren’t experts at this stuff, because I know some of you never worked for law enforcement. But if anyone in your family who has worked in law enforcement, I will appreciate their help too. Thank you so much. Nice comments only. I will remove and block to the ones are considered rude and offensive. Just a girl who never worked in law enforcement needing help on their book.