Zechariah son of Barachiah appears as a conflation of 2 Chronicles 24:20-22, Zechariah 1:1 and Josephus' Zechariah son of Baruch/Baris killed in the temple in 68 AD:
The Murder of Zacharias
War 4.5.4 335-344
And now these Zealots and Idumaeans were quite weary of simple massacre, so they had the audacity to set up mock trials and courts of justice for that purpose. They intended to have Zacharias, the son of Baris, one of the most eminent of the citizens, slain. What provoked them against him was that hatred of wickedness and love of liberty which were so eminent in him; he was also a rich man, so that by taking him off, they did not only hope to seize his effects, but also to get rid of a man that had great power to destroy them.
So they called together, by a public proclamation, seventy of the principal men of the populace, for a show trial, as if they were real judges, although they had no proper authority. In front of these citizens Zacharias was accused of a design to betray their city to the Romans and to have traitorously sent to Vespasian for that purpose. Now there appeared no proof or sign of what he was accused; but they affirmed themselves that they were well persuaded that so it was, and desired that such their affirmation might be taken for sufficient evidence.
Now when Zacharias clearly saw that there was no way remaining for his escape from them, as having been treacherously called before them and imprisoned, but with no intention of a legal trial, he took great liberty of speech in that despair of life he was under. Accordingly he stood up, and laughed at their pretended accusation, and in a few words confuted the crimes laid to his charge; after which he turned his speech to his accusers, and went over distinctly all their transgressions of the Law, and made heavy lamentations upon the confusion they had brought public affairs into.
In the meantime the Zealots grew tumultuous, and could scarce refrain from drawing their swords, although they designed to preserve the appearance and show of judicature to the end. They were also desirous, on other accounts, to try the judges, whether they would be mindful of what was just at their own peril.
Now the seventy judges brought in their verdict, that the person accused was not guilty -- choosing rather to die themselves with him, than to have his death laid at their doors.
Hereupon there arose a great clamor by the Zealots upon his acquittal, and they were all indignant at the judges for not having understood that the authority that was given them was but in jest. So two of the boldest of them fell upon Zacharias in the middle of the Temple, and slew him. And as he fell down dead they bantered him, and said, "Now you have our verdict also, and a surer release." They then threw him down out of the Temple into the valley beneath it.