Raphael painted him, but, who's Heliodorus?

Raffaello, The Expulsion of Heliodorus from the Temple, 1511-12, Vatican Museums

Raphael painted this scene in the Apartments of Pope Julius the II in 1511-12,  this fresco is one of the most admired masterpieces of the Vatican Museums. Every day more than 1000 tourists are observing and studying the characters, the colors, the composition.
But what does this scene rapresent? Who is Heliodorus?
The story is a biblical episode (2 Maccabees 3). This is what is written:

The story of Heliodorus

3 When the holy city was living in harmony, and people observed the laws rigorously because of Onias the high priest, who was devoted to God and hated evil, ² the kings used to honor the place and glorify the temple by sending the best gifts. ³ Seleucus the king of Asia even supplied all expenses for the sacrificial service from his own revenues. ⁴ But a certain Simon from the tribe of Benjamin, who had been appointed administrator of the temple, had a difference of opinion with the high priest about the management of the city market. ⁵ Since he wasn’t able to overcome Onias, he went to Thraseas’ son Apollonius, who was governor of Coele-Syria and Phoenicia at that time. ⁶ Simon told him that the treasury in Jerusalem was filled with untold riches and that it was full of uncounted cash, which didn’t belong to the accounts for the sacrifices, but potentially fell under the king’s authority. ⁷ Apollonius met with the king and told him about the funds.

The king chose his chief administrator Heliodorus and sent him with orders to confiscate the funds in question. ⁸ Heliodorus immediately made the journey, supposedly to inspect the cities of Coele-Syria and Phoenicia but actually to put the king’s plan into effect. ⁹ When he arrived in Jerusalem and was received in a friendly manner by the high priest of the city, he revealed the information that had been reported and stated plainly why he had come. Then he asked whether these things were true. ¹⁰ The high priest informed him that these were the deposits of widows and orphans, ¹¹ and also some deposits of Hyrcanus the Tobiad, an exceedingly prominent man. He also said that there were only 22,800 pounds of silver and 11,400 pounds of gold, and that the ungodly Simon had given a false report. ¹² It was wholly unthinkable, he added, to commit such an injustice against those who trusted in the holiness of the place and in the dignity and sacredness of the temple that is honored throughout the whole world. ¹³ But Heliodorus, because of the royal commands, was firm that in any case the king could take these funds. ¹⁴ So he set a date and proceeded to inspect these funds. This caused great agony throughout the whole city. ¹⁵ But the priests threw themselves down before the altar in their priestly robes and called to heaven to the one who had given the laws about such deposits, that he should keep the deposits safe. ¹⁶ Anyone seeing the outward appearance of the high priest would have been heartbroken, because his expression and changed color revealed his inner anguish. ¹⁷ Fear and trembling seized the man, making the grief lodged in his heart clear to observers. ¹⁸ People burst from their houses in crowds to plead for help because the temple^[a] was about to be dishonored. ¹⁹ With mourning clothes wrapped beneath their breasts, women filled the streets. The virgins, who usually remained indoors, ran together to the gates and some to the walls, while others peeped through their windows. ²⁰ But all raised up their hands to heaven and pleaded for help. ²¹ To see the whole crowd on its knees and faces and the great suffering and dread of the high priest was a pitiful sight. ²² So they called on the almighty Lord to protect the deposits for those who had entrusted them.
²³ But Heliodorus carried on with what had been decided. ²⁴ When he and his spearmen approached the treasury, however, the ruler of all spirits and all authority made an awesome display, so that all those daring to come with Heliodorus fainted, terrified and awestruck by God’s power. ²⁵ A horse appeared to them with a fearsome rider and decked out with a beautiful saddle. While running furiously, the horse attacked Heliodorus with its front hooves. The rider appeared to be clothed in full body armor made of gold. ²⁶ Two young men also appeared before him—unmatched in bodily strength, of superb beauty, and with magnificent robes. They stood on either side of Heliodorus and beat him continuously with many blows. ²⁷ When he suddenly fell to the ground unconscious, his men grasped him and placed him on a stretcher. ²⁸ This was the same man who had just entered the treasury with a large group of men and a full bodyguard. Now they carried him away helpless, despite his weapons, and they publicly acknowledged God’s power. ²⁹ While he was being cut down and left speechless through the divine power and deprived of all hope of recovery, ³⁰ the people were praising the Lord for acting miraculously on behalf of his holy place. And the temple, which had been weighed down with fear and disturbance a short time earlier, was now filled with delight and joy because the almighty Lord had publicly appeared.

³¹ Some of Heliodorus’ companions rushed to ask Onias to pray to the Most High to give life to the one who was about to draw his last breath. ³² The high priest, fearful that perhaps the king might think that the Jews had done something evil to Heliodorus, offered a sacrifice for the man’s recovery.
³³ While the high priest was making the sacrifice for reconciliation, the same two^[b] young men, dressed in the same clothing, appeared again to Heliodorus. They stood by him and said, “You owe Onias the high priest your gratitude. Because of him the Lord has graciously given life to you. ³⁴ But you who suffered a beating from heaven must proclaim the great power of God to all.” Once they said these things, they disappeared.
³⁵ Heliodorus offered a sacrifice to the Lord and made many solemn promises to the savior for sparing his life. After thanking Onias, he took his military force back to the king. ³⁶ He testified to everyone about the works of the great God that he had seen with his own eyes. ³⁷ When the king asked Heliodorus who would be the right sort of person to send again to Jerusalem, he said: ³⁸ “If you have an enemy or someone plotting against your government, send him, and he will come back badly beaten if he should come back at all, because some divine power truly surrounds the temple.^{[c] 39} The one who lives in heaven watches over that place and will strike and destroy anyone coming with evil intent.” ⁴⁰ So this is how matters turned out concerning Heliodorus and the guarding of the treasury.