Many languages distinguish between inclusive and exclusive first-person plural pronouns (“we”). (Click or tap here to see more details)
The inclusive “we” specifically includes the addressee (“you and I and possibly others”), while the exclusive “we” specifically excludes the addressee (“he/she/they and I, but not you”). This grammatical distinction is called “clusivity.” While Semitic languages such as Hebrew or most Indo-European languages such as Greek or English do not make that distinction, translators of languages with that distinction have to make a choice every time they encounter “we” or a form thereof (in English: “we,” “our,” or “us”).
For this verse, translators typically select the inclusive form (including Aaron).
In Huautla Mazatec, however, the translators selected the exclusive pronoun (excluding Aaron).
In the Karbi and the Tok Pisin translations, for the first part of the verse the inclusive pronoun is used (including Aaaron) but for the last part (“we do not know what has happened to him” in English) the exclusive pronoun is used (excluding Aaron).
Source: Velma Pickett and Florence Cowan in Notes on Translation January 1962, p. 1ff. and W. R. Hutton in The Bible Translator April 1953, p. 86ff. (Karbi).