"Once we have collected more information, we will be prepared to respond appropriately," Rubio told reporters on Thursday night, local time in Sweden.
Cuba's Interior Ministry said the motorboat was in Cuban waters and fired on the coast guard as it approached to identify it. Four people were killed and six were injured when the coast guard returned fire. Their nationalities are not known.
According to Reuters, Rubio said the motorboat was not part of an American operation and that no government employees were on board.
