Peter and the other disciple went is literally “Peter left (a singular verb) and the other disciple, and they went.” The verb structure is similar to that discussed in 2.2 (see there). Though the verb form is singular, it is obvious that both Peter and the other disciple are included in the action.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .