Here the word "their" refers to the Jewish people as a whole.
# It came about ... that
This phrase is used here to mark where the action starts. If your language has a way for doing this, you could consider using it here.
# their rulers, elders and scribes
This is a reference to the Sanhedrin, the Jewish ruling court, which consisted of these three groups of people. (See: [[rc://en/ta/man/translate/figs-synecdoche]])
# John, and Alexander
These two men were members of the high priest's family. This is not the same John as the apostle.