An undated photo from a social media account of Omar Mateen, who Orlando Police have identified as the suspect in the mass shooting at a gay nighclub in Orlando, Florida, U.S., June 12, 2016. Omar Mateen via Myspace/Handout via REUTERS

WASHINGTON (Reuters) - Omar S. Mateen, the Florida resident suspected of killing 50 people at a gay nightclub in Orlando, Florida, called 911 before the shooting and swore allegiance to Islamic State, NBC News said on Twitter.

In a posting on its web site, MSNBC said Mateen swore allegiance to Islamic State leader Abu Bakr al-Baghdadi.