BOSTON — A Massachusetts man pleaded guilty on Monday to charges that he threatened to kill Jews and bomb a synagogue in a case that U.S. prosecutors said reflected a growing nationwide torrent of antisemitism after the Israel-Hamas war in Gaza began last year.

John Reardon, during a hearing in Boston federal court, pleaded guilty to threatening to bomb the Congregation Agudas Achim and threatening to kill children in a voicemail he left with the Attleboro, Massachusetts-based synagogue…