And this was done by public vote of the city. And when they accepted, because they wished to live peaceably and suspected nothing, the men of Joppa took them out to sea and drowned them, not less than two hundred: Joppa was a Gentile city, and the Jews were not official citizens. When the citizens, by public vote, invited the Jews along with them for a cruise, they accepted. This was done by public vote of the city is probably mentioned in order to make the reader aware that the whole city was guilty of the atrocity, not just the men on the boats. It may be helpful to put this clause in proper chronological order with the rest of the text by combining verses 3 and 4 as follows:

• About this time, the people of the seaside city of Joppa did a cruel thing to the local Jews. After a public vote, they invited all the Jews—men, women, and children—to join them in a boat ride, using boats that the townspeople owned. The Jews had no reason to suspect anything, and since they wanted to be good neighbors, they accepted the invitation. The men of Joppa took them out to sea on the boats, and drowned them. At least two hundred people died.

Some translators may wish to keep the sequence of clauses as in Revised Standard Version. Contemporary English Version provides a good model that does this, using direct speech:

• 3 The people of Joppa also committed a terrible crime against their Jewish neighbors. They pretended to be on good terms with them and said, “We want you and your families to go sailing with us. We’ll provide the ships.”
4 They accepted this invitation since the whole town of Joppa had voted to invite them. Besides, they wanted to be on good terms with the Gentiles and didn’t suspect a plot. But when the ships reached the open sea, the people of Joppa drowned about two hundred of the Jews.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Maccabees. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here.