From the Founding of the City/Book 12

[Y.R. 469. B.C. 283.] The Senonian Gauls having slain the Roman ambassadors, war is declared against them: they cut off L. Caecilius, praetor, with the legions under his command, [Y.R. 470. B.C. 282.] The Roman fleet plundered by the Tarentines, and the commander slain: ambassadors, sent to complain of this outrage, are ill-treated and sent back; whereupon war is declared against them. The Samnites revolt; against whom, together with the Lucanians, Bruttians, and Etruscans, several unsuccessful battles are fought by different generals. [Y.R. 471. B.C. 281.] Pyrrhus, king of Epirus, comes into Italy, to succour the Tarentines. A Campanian legion, sent, under the command of Decius Jubellius, to garrison Rhegium, murder the inhabitants, and seize the city.

Ab Urbe Condita - Periochae/liber XII