Well the Rossetti's are well known in Cosa Nostra circles to the FBI. Mark's father Ralph was a made guy in East Boston who ran with J.R Russo's crowd. Then Mark and his cousins Stephen and Michael became heavily involved in armored car robbing, general theft, and having dangerous and violent reputations. Stephen Rossetti, David Turner, and Carmello Merlino were three suspects in the Isabella Stewart Gardner Museum heist. Then of course Darin Bufalino got involved, and then everyone got enlisted to work with Boss Frank Salemme. And of course the FBI isnt stupid, they know Mark didnt get his stripes because he was an earner, he got it because him and Darin can put people to sleep. Plus they knew he was a heroin junkie...