So Dio Cassius wrote:
[In the year 217] the hunting theatre was struck by thunderbolts on the very day of the Vulcanalia, and such a blaze followed that its entire upper circuit and everything in the arena was consumed, and thereupon the rest of the structure was ravaged by the flames and reduced to ruins. Neither human aid could avail against the conflagration, though practically every aqueduct was emptied, nor could the downpour from the sky, which was most heavy and violent, accomplish anything — to such an extent was the water from both sources consumed by the power of the thunderbolts, and, in fact, actually contributed in a measure to the damage done. In consequence of this disaster the gladiatorial show was held in the stadium for many years. (Dio Cass., 78, 25).

The fire, like others that took place during Macrinus reign, was considered as an ominous foreboding, announcing the forthcoming death of the emperor, who had dared suppress the horse races dedicated to the god Vulcanus. The god had taken his vengeance right in the day dedicated to him.

DIO CASSIUS, full name DIO CASSIUS COCCEIANUS (c. 150-235), Roman historian and politician, born in Nicaea, in Bithynia; his maternal grandfather was the Stoic philosopher Dion Chrysostomus (c. 40-112). Dio Cassius held office in Rome under the emperors Commodus, Pertinax (126-93), Septimius Severus, and Alexander Severus (208-35); he twice attained (220 and 229) the consulship. Dio Cassius is best known as the author of a history of Rome in 80 books, written in Greek. Only 18 are extant in their entirety, but fragments of some of the others and epitomes by later writers have been preserved. All are of primary importance for the history of the last years of the Roman Republic and the first years of the Roman Empire. The name Dio Cassius is sometimes also spelled Dion Cassius.