Washington: In a first for the US, social networking giant Facebook on Sunday activated its Safety Check feature for users in the aftermath of the the mass shooting at a gay nightclub in Florida in which at least 50 people were killed and 53 others injured.
The feature allows people to notify their friends if they are in the affected area and mark themselves as safe.
A click or tap on the "I'm Safe" button lets friends and loved ones know straight away. Users can also check to see whether their friends are safe too.
The gunman, named by officials as Afghan-origin Omar Mateen, 29, was killed by a SWAT team after he took hostages at Pulse, a popular gay night club.
It is believed that the suspect, who was a US citizen from the Florida town of Port St Lucie, was not on a terrorism watch list, although he was being investigated for an unrelated criminal act, BBC reported.
US President Barack Obama called the mass shooting an "act of terror" and "act of hate".
Facebook's Safety Check feature, launched in October 2014, has now been deployed on several occasions including the terrorist attacks in Paris.