Probably both: to shame Frankie for breaking omerta, and to pose a visible threat. Others here have found earlier script references to Frankie having a family in Sicily (in addition to his brother) who'd be vulnerable if he stood by his affidavit.
Ntra la porta tua lu sangu � sparsu,
E nun me mporta si ce muoru accisu...
E s'iddu muoru e vaju mparadisu
Si nun ce truovo a ttia, mancu ce trasu.
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