|Source: National Geographic-|
The Irish Mob was a big deal in the Northeast in the 1960s, 70s and 80s but have had similar problems that the Italian Mob has had the last twenty years. They've lost most of their leadership to the FBI and US Attorneys and a lot of them are now in prison and doing long sentences if not life sentences. People like James Whitey Bulger, as well Irish hitman Mike Mad Dog Sullivan, who'll probably never get out of prison, even though he wasn't officially sentenced to life. And the Irish Mob has kept alive the Irish stereotype that the Irishman have short and vicious tempers.
Irish mobsters are known for fighting and killing and actually enjoy doing those things. Mad Dog Sullivan is responsible for killing somewhere in the neighborhood of hundred people. You aren't able to kill that many people, if for one you aren't good at it, meaning you pull it off and get away with it. But also if you don't mind doing it, especially if you are killing bad people. People who have killed and have hurt innocent people on purpose. Italian mobsters kill for business, but Irish mobsters seem to enjoy killing people, something that has set Irish gangs apart.