EDITOR'S NOTE: Orlando's mayor on Monday revised the death toll in the nightclub shooting to 49, from 50. The 50th body was identified as gunman Omar Mateen.

Facebook activated its Safety Check service for the first time in the U.S. after Sunday morning’s deadly shooting in a packed Orlando nightclub that killed 50 people and wounded at least 53 more.

ISIS claimed responsibility for the attack Sunday afternoon via its Amaq news agency, according to Reuters.

Designed for times of disaster or crisis, Safety Check lets users in a specific area notify friends and family that they are safe. Users can also check on others in the affected area and mark friends as safe.

Related: Belgians harness social media to help people affected by Brussels terror attacks

The social network activated its Safety Check feature following the Brussels terror attacks and the bombing in Ankara, Turkey earlier this year, as well as the attacks that rocked Paris last year.

Earlier this year Facebook apologized for a glitch in its Safety Check service that sent out misdirected notifications after the Easter Sunday bombing that killed 70 people in Lahore, Pakistan.

The shooting at Orlando gay club Pulse dominated social media Sunday, with #Orlando the top trending U.S. topic on Twitter. News coverage of the attack also appeared in Facebook’s Trending Topics section.

Follow James Rogers on Twitter @jamesjrogers