These are the headlines you Need2Know:
Trump Threatens Iran on Twitter: President Trump lashed out against Iranian President Hassan Rouhani late Sunday, warning him -- in an all-caps tweet -- to "never, ever threaten the United States again or you will suffer the consequences the likes of which few throughout history have ever suffered before." His tweet comes in response to Rouhani's warning to Trump that "war with Iran is the mother of all wars." Read the details on NPR.
Deadly Shooting in Toronto: Two people died and a dozen others were wounded in Toronto after a shooter opened fire in a popular neighborhood late Sunday. Neither of the victims has been identified. Authorities say the gunman is also dead, and they are now investigating the motive behind the shooting. Read the latest on CNN.
Mourning Boat Accident Victims: The 17 victims of the duck boat accident in Missouri were remembered in a service on Sunday near the site of the accident. The memorial came as federal investigators are examining the boat's black box and video footage. Read more at CBS News.
Italian Wins the British Open: Francesco Molinari claimed the Claret Jug on Sunday, becoming the first Italian to win a major. He outlasted Tiger Woods, Jordan Spieth, Rory McIlroy and others to secure the prize. Read more at BBC.
Cheddar's Hope King gets into the latest.
Subscribe to the Need2Know newsletter here.