Titus Livius (Livy), The History of Rome, Book 39
Evan T. Sage, Ph.D., Ed.

34. When these embassies had been dismissed, Philip was informed by his representatives that he was to retire from the cities and withdraw his garrisons; being angered at everyone, he vented his wrath on the Maroneans. [2] He sent word to Onomastus, who was in command of the sea coast, to kill the leading men of the opposing party. Onomastus, through the agency of a certain Casander, one of the king's supporters who had long been a resident of Maronea, admitting the Thracians by night, caused a slaughter as if the town had been captured in war. [3] When the Roman commissioners complained of such cruel treatment of the unoffending Maroneans and of such arrogant conduct towards the Roman people, that those men whose liberty the senate had declared was to be restored were murdered as if they were enemies, Philip in reply denied that any of this concerned himself or any one of his subjects; [4] there had been fighting as a consequence of internal strife, since some were for transferring the city to him, others to the Romans; [5] this fact they could easily ascertain; let them, he said, question the Maroneans themselves —not doubting that when all were smitten with the terror of so recent a massacre no one would dare to open his mouth against him. [6] Appius replied that so clear a case needed no investigation as if it were not clear. If Philip wished to avert blame from himself he should send Onomastus and Casander, through whom it was said that the plan had been executed, to Rome, in order that the senate might question them. [7] This speech at first so disconcerted the king that he could not control his colour or [p. 327]expression; then, at length collecting his wits, he¹ said that he would send Casander, who had been at Maronea, if they really wished it; [8] but how did this affair concern Onomastus, who had not only not been at Maronea but had not even been in any district close to it? [9] And in fact he was both careful to spare Onomastus, as a more valued friend, and was likewise much more afraid of him as an informer, because he himself had exchanged views with him and used him as an agent and accomplice in many such affairs. [10] Casander, moreover, when men were sent to conduct him through Epirus to the sea, was believed to have been done away with by poison, lest in some way his evidence might get out.²