On the final night of the Democratic National Convention, Mary Bruce has details on Vice President Kamala Harris' historic speech as she becomes the first woman of color to accept a major party's nomination for president; Pierre Thomas reports as law enforcement take an Arizona man into custody who allegedly threatened to kill former Pres. Trump on social media; James Longman has the latest after dive teams recovered the body of the British tech tycoon whose superyacht sank off the Sicilian coast; and more on tonight's broadcast of World News Tonight with David Muir.