Herodian (late second, first half third century): Greek historian, author of a History of the Roman Empire since the Death of Marcus Aurelius in which he describes the reign of Commodus (180-192), the Year of the Five Emperors (193), the age of the Severan dynasty (211-235), and the Year of the Six Emperors (238).
The translation was made by Edward C. Echols (Herodian of Antioch's History of the Roman Empire, 1961 Berkeley and Los Angeles) and was put online for the first time by Roger Pearse (Tertullian.Org). The version offered on these pages is hyperlinked and contains notes by Jona Lendering.
Murder of Heliogabalus
[5.8.1]  With everything that formerly had been held sacred being done in a frenzy of arrogance and madness, all the Romans, especially the praetorians, were angered and disgusted. They were annoyed when they saw the emperor, his face painted more elaborately than that of any modest woman, dancing in luxurious robes and effeminately adorned with gold necklaces.
[5.8.2] As a result, they were more favorably disposed toward Alexander, for they expected great things of a lad so properly and modestly reared. They kept continual watch upon the youth when they saw that Heliogabalus was plotting against him. His mother Mamaea did not allow her son to touch any food or drink sent by the emperor, nor did Alexander use the cupbearers or cooks employed in the palace or those who happened to be in their mutual service; only those chosen by his mother, those who seemed most trustworthy, were allowed to handle Alexander's food.
[5.8.3] Mamaea secretly distributed money to the praetorians to win their good will for her son; it was to gold that the praetorians were particularly devoted. When he learned this, Heliogabalus plotted against Alexander and his mother in every conceivable way, but Maesa, the grandmother of them both, foiled all his schemes; she was astute in every way and had spent much of her life in the imperial palace. As the sister of Severus' wife Julia, Maesa had always lived with the empress at the court.
[5.8.4] Therefore, none of Heliogabalus' schemes escaped her attention, for the emperor was careless by nature, and his intrigues were always obvious. Since his plots failed, the emperor undertook to strip Alexander of the honor of caesar, and the youth was no longer to be seen at public addresses or in public processions.
[5.8.5] [11 or 12 March 222] But the soldiers called for Alexander and were angry because he had been removed from his imperial post. Heliogabalus circulated a rumor that Alexander was dying, to see how the praetorians would react to the news. When they did not see the youth, the praetorians were deeply grieved and enraged by the report; they refused to send the regular contingent of guards to the emperor and remained in the camp, demanding to see Alexander in the temple there.
[5.8.6] Thoroughly frightened, Heliogabalus placed Alexander in the imperial litter, which was richly decorated with gold and precious gems, and set out with him for the praetorian camp. The guards opened the gates and, receiving them inside, brought the two youths to the temple in the camp.
[5.8.7] They welcomed Alexander with enthusiastic cheers, but ignored the emperor. Fuming at this treatment, although he spent the night in the camp, Heliogabalus unleashed the fury of his wrath against the praetorians. He ordered the arrest and punishment of the guards who had cheered Alexander openly and enthusiastically, pretending that these were responsible for the revolt and uproar.
[5.8.8] The praetorians were enraged by this order; since they had other reasons, also, for hating Heliogabalus, they wished now to rid themselves of so disgraceful an emperor, and believed, too, that they should rescue the praetorians under arrest. Considering the occasion ideal and the provocation just, they killed Heliogabalus and his mother Soaemias (for she was in the camp as Augusta and as his mother), together with all his attendants who were seized in the camp and who seemed to be his associates and companions in evil.
[5.8.9] They gave the bodies of Heliogabalus and Soaemias to those who wanted to drag them about and abuse them; when the bodies had been dragged throughout the city, the mutilated corpses were thrown into the public sewer which flows into the Tiber.
[5.8.10] After having ruled the empire for more than five years,note[Little less than four years, actually: from 16 May 218 to 11/12 March 222.] leading the kind of life described above, Heliogabalus perished in this manner together with his mother. The praetorians then proclaimed Alexander emperor and conducted him into the palace while he was still a youth and still being given a thorough education by his mother and his grandmother.