Families still took their children trick-or-treating in lower Manhattan. And costumed New Yorkers flooded the streets for an annual Halloween parade.
Officials told reporters the attack started Sunday night in the country's capital and lasted several hours.
Police say a 49-year-old man opened fire at an upscale apartment complex pool Sunday evening.
Police have revised the death toll for the attack near U.K.'s Parliament from five to four, including the attacker.
Multiple tornadoes touched down in the New Orleans area Tuesday and damaged hundreds of buildings.
Canadian authorities say Alexandre Bissonnette is facing six counts of first-degree murder and five counts of attempted murder.
According to police, two gunmen opened fire inside the Quebec City Islamic Cultural Centre on Sunday night.
At least 20 people were killed over the weekend as tornadoes tore through the Southeast. In 2016, a total of 17 people were killed by twisters.
The suspect was taken into custody during a police raid in Istanbul's Esenyurt district. Authorities had been tracking him for more than two weeks.
Chicago police said they investigated 27 shooting incidents that left at least 12 people dead and dozens of others wounded.
The Denver Police Department is investigating a shooting early Sunday at 14th and Market Streets.
Turkish officials say at least 34 people have been killed and 125 injured in a car bomb explosion in Ankara.