Livy said this quote
“ At last he was to feel that he had the town, as it were, in his pocket, and was ready for anything. Accordingly he sent a confidential messenger to Rome, to ask his father what step he should next take, his power in Gabii being, by God's grace, by this time absolute. Tarquin, I suppose, was not sure of the messenger's good faith: in any case, he said not a word in reply to his question, but with a thoughtful air went out to the garden. The man followed him, and Tarquin, strolling up and down in silence, began knocking off poppy-heads with his stick. The messenger at last wearied of putting his question and waiting for the reply, so he returned to Gabii supposing his mission to have failed. He told Sextus what he had said and what he had seen his father do: the king, he declared, whether from anger, or hatred, or natural arrogance, had not uttered a single word. Sextus realized that though his father had not spoken, he had, by his action, indirectly expressed his meaning clearly enough; so he proceeded at once to act upon his murderous instructions. ”