Which kind of 'mafia' took Willis' family hostage ?
Which 'mysterious' crime syndicate was that ?
We can already rule out any of the Asians, Caribbeans/Afro-Americans/Africans, Ex-Sovjets, Pacifics and Latinos/Hispanics.
That leaves us with the Italians, the Irish, the Dixie Mafia or those White Supremacist crime syndicates ( Aryan Brotherhood for instance ). AB seems very unlikely, so my bet's on Italians, Irish or Dixies.