Ammianus Marcellinus Res Gestae 14.2.2

[2] And, in the words of Cicero, ¹ as even wild animals, when warned by hunger, generally return to the place where they were once fed, so they all, swooping like a whirlwind down from their steep and rugged mountains, made for the districts near the sea; and hiding themselves there in pathless lurking-places and defiles as the dark nights were coming on-the moon being still crescent and so not shining with full brilliance—they watched the sailors. And when they saw that they were buried in sleep, creeping on all fours along the anchor-ropes and making their way on tiptoe into the boats, they came upon the crew all unawares, and since their natural ferocity was fired by greed, they spared no one, even of those who surrendered, but massacred them all and without resistance carried off the cargoes, led either by their value or by their usefulness.