Titus Livius (Livy), The History of Rome, Book 5
Rev. Canon Roberts, Ed.

41. After all the arrangements that circumstances permitted had been made for the defence of the Capitol, the old men returned to their respective homes and, fully prepared to die, awaited the coming of the enemy. [2] Those who had filled curule offices resolved to meet their fate wearing the insignia of their former rank and honour and distinctions. They put on the splendid dress which they wore when conducting the chariots of the gods or riding in triumph through the City, and thus arrayed, they seated themselves in their ivory chairs in front of their houses. [3] Some writers record that, led by M. Fabius, the Pontifex Maximus, they recited the solemn formula in which they devoted themselves [4??] to death for their country and the Quirites.

As the Gauls were refreshed by a night's rest after a battle which had at no point been seriously contested, and as they were not now taking the City by assault or storm, their entrance the next day was not marked by any signs of excitement or anger. Passing the Colline gate, which was standing open, they came to the Forum and gazed round at the temples and at the Citadel, which alone wore any appearance of war. [5] They left there a small body to guard against any attack from the Citadel or Capitol whilst they were scattered, and then they dispersed in quest of plunder through streets in which they did not meet a soul. Some poured in a body into all the houses near, others made for the most distant ones, expecting to find them untouched and full of spoils. [6] Appalled by the very desolation of the place and dreading lest some stratagem should surprise the stragglers, they returned to the neighbourhood of the Forum in close order. [7] The houses of the plebeians were barricaded, the halls of the patricians stood open, but they felt greater hesitation about entering the open houses than those which were closed. [8] They gazed with feelings of real veneration upon the men who were seated in the porticoes of their mansions, not only because of the superhuman magnificence of their apparel and their whole bearing and demeanour, but also because of the majestic expression of their countenances, wearing the very aspect of gods. [9] So they stood, gazing at them as if they were statues, till, as it is asserted, one of the patricians, M. Papirius, roused the passion of a Gaul, who began to stroke his beard —which in those days was universally worn long —by smiting him on the head with his ivory staff. He was the first to be killed, the others were butchered in their chairs. [10] After this slaughter of the magnates, no living being was thenceforth spared; the houses were rifled, and then set on fire.