10 Things to Know for Tuesday

Omar Mateen, who killed 49 people at the club in Orlando, Florida, claimed to support Islamic State extremists, as well opposing groups such as Hezbolla and Nusra Front. Large crowds gather for the "OneOrlando Vigil" in the city where the rampage occurred, while other memorials are being held across the country. Officials scrutinized Omar Mateen for making radical, violent statements in 2013, then investigated him again in 2014 because he was casually acquainted with a suicide bomber. Donald Trump vows to impose bans on immigrants from parts of the world associated with terrorism, while Hillary Clinton warns that demonizing all Muslims would only play into the hands of extremists. Former British Prime Minister Gordon Brown calls for Labour Party supporters to vote to stay in the European Union.