Facebook on Sunday activated its Safety Check feature for the first time in the U.S., in the aftermath of the mass shooting at an Orlando night club that left 49 people dead and scores more wounded. Last year's terrorist attacks in Paris marked the first time Facebook activated the feature for a crisis other than a natural disaster. Safety Check lets users notify loved ones and friends that they're safe. Users can check on people thought to be in the affected area, and mark friends and loved ones as safe when they receive confirmation.