וְצָד֧וֹק בֶּן־אֲחִיט֛וּב וַאֲבִימֶ֥לֶךְ בֶּן־אֶבְיָתָ֖ר כֹּהֲנִ֑ים וְשַׁוְשָׁ֖א סוֹפֵֽר׃
And Zadok the son of Ahitub, and Abimelech the son of Abiathar, were priests; and Shavsha was scribe;
Rashi on I Chronicles
and Shavsha was scribe Ahilud was the recorder, and Shavsha would write alongside him.