The identity of the youth is discussed in the Talmud. He is identified as the angel Gabriel. Gabriel was told to deliver a judgment upon the enemies of the Jews (which the sages say actually refers to the unrighteous Jews themselves). Gabriel receives lashes because he was not obedient in the way he delivered the judgment. He was to gather some coals and cast them in judgment directly from his own hands. Instead, a cherub handed them to him that allowed the coals of the fire of judgment to cool. Also, he said directly that he delivered the judgment when he KNEW that you never speak directly about something so dreadful as a judgment. Because the cherub handled the judgment coal it had cooled before Gabriel cast it into the land, and thus there were some Jewish survivors. This is all predictive of 70 AD. He was beaten with many stripes from a flaming sword. In his absence a Persian angel steps into his place. Michael helps the Persian angel.
...The Holy One, Blessed be He, said to Michael, the ministering angel of the Jewish people: Michael, your nation has sinned (see Daniel 10:21). He replied: Master of the Universe, may it be enough for the good people among them to save them from destruction. He said to him: I will burn them and the good among them because the good do not rebuke the wicked. Immediately, God spoke to Gabriel: “He spoke to the man clothed in linen and said: Go in between the wheelwork and beneath the cherub, and fill your hands with coals of fire from between the cherubs, and scatter them over the city; and he came before my eyes” (Ezekiel 10:2). Immediately: “And the cherub stretched out his hand from between the cherubs into the fire that was between the cherubs, and took and put it into the hands of him that was clothed in linen [IE: Gabriel], who took it and went out” (Ezekiel 10:7).
You can read the rest of the account at this link.
Gabriel may also be the mysterious youth in Mark:
[Mar 14:50-52 NLT] (50) Then all his disciples deserted him and ran away. (51) One young man following behind was clothed only in a long linen shirt. When the mob tried to grab him, (52) he slipped out of his shirt and ran away naked.
That the "young man" that shows up repeatedly is actually an angel is made clearer by the account of the rolling away of the stone from Jesus' tomb:
[Mar 16:1-8 NLT] (1) Saturday evening, when the Sabbath ended, Mary Magdalene, Mary the mother of James, and Salome went out and purchased burial spices so they could anoint Jesus' body. (2) Very early on Sunday morning, just at sunrise, they went to the tomb. (3) On the way they were asking each other, "Who will roll away the stone for us from the entrance to the tomb?" (4) But as they arrived, they looked up and saw that the stone, which was very large, had already been rolled aside. (5) When they entered the tomb, they saw a young man clothed in a white robe sitting on the right side. The women were shocked, (6) but the angel said, "Don't be alarmed. You are looking for Jesus of Nazareth, who was crucified. He isn't here! He is risen from the dead! Look, this is where they laid his body. (7) Now go and tell his disciples, including Peter, that Jesus is going ahead of you to Galilee. You will see him there, just as he told you before he died." (8) The women fled from the tomb, trembling and bewildered, and they said nothing to anyone because they were too frightened. [Shorter Ending of Mark] Then they briefly reported all this to Peter and his companions. Afterward Jesus himself sent them out from east to west with the sacred and unfailing message of salvation that gives eternal life. Amen.
So he was both a "young man" and an angel!
However, Jesus alludes to the prophecy of Gabriel and indicates that he is going to fulfill even this scripture. He will, from his own hot hands cast the fire of the unmitigated wrath of God upon his enemies, his unregenerate People:
[Luk 12:49 ESV] (49) "I came to cast fire on the earth, and would that it were already kindled!
We see this come to pass in 70 AD in the Revelation. Since Gabriel was disobedient per the Talmud he is replaced with Michael. However, we know from Luke that this is actually the Messiah, Jesus. Notice that the coals of wrath come directly from the Michael's/Jesus' hand:
[Rev 8:3-5 KJV] (3) And another angel came and stood at the altar, having a golden censer; and there was given unto him much incense, that he should offer it with the prayers of all saints upon the golden altar which was before the throne. (4) And the smoke of the incense, which came with the prayers of the saints, ascended up before God out of the angel's hand. (5) And the angel took the censer, and filled it with fire of the altar, and cast it into the earth: and there were voices, and thunderings, and lightnings, and an earthquake.
Gabriel also appears to Zechariah the priest as he officiates at the altar during Yom Kippur, further associating him with the altar and the name "Zechariah":
[Luk 1:8-20 NLT] (8) One day Zechariah was serving God in the Temple, for his order was on duty that week. (9) As was the custom of the priests, he was chosen by lot to enter the sanctuary of the Lord and burn incense. (10) While the incense was being burned, a great crowd stood outside, praying. (11) While Zechariah was in the sanctuary, an angel of the Lord appeared to him, standing to the right of the incense altar. (12) Zechariah was shaken and overwhelmed with fear when he saw him. (13) But the angel said, "Don't be afraid, Zechariah! God has heard your prayer. Your wife, Elizabeth, will give you a son, and you are to name him John. (14) You will have great joy and gladness, and many will rejoice at his birth, (15) for he will be great in the eyes of the Lord. He must never touch wine or other alcoholic drinks. He will be filled with the Holy Spirit, even before his birth. (16) And he will turn many Israelites to the Lord their God. (17) He will be a man with the spirit and power of Elijah. He will prepare the people for the coming of the Lord. He will turn the hearts of the fathers to their children, and he will cause those who are rebellious to accept the wisdom of the godly." (18) Zechariah said to the angel, "How can I be sure this will happen? I'm an old man now, and my wife is also well along in years." (19) Then the angel said, "I am Gabriel! I stand in the very presence of God. It was he who sent me to bring you this good news! (20) But now, since you didn't believe what I said, you will be silent and unable to speak until the child is born. For my words will certainly be fulfilled at the proper time."
The prayers are not prayers for Jerusalem's safety but rather that the saints that the Jews are persecuting will be avenged by wrath. The much incense that Jesus adds to their prayers are those of the prophets murdered by the Jews from the beginning of Jerusalem. It was to all fall upon this generation in 70 AD.