In one of the worst mass shootings in US history, a gunman believed to be inspired by the Islamic State in Iraq and Syria (ISIS) opened fire on a popular gay nightclub in Orlando on June 12, Sunday, killing at least 50 people and injuring 53 more.

The gunman, 29-year-old Omar Mir Sedique Mateen of Fort Pierce Florida, opened fire inside Pulse Club around 2 AM during its "Latin Night", CNN reported. After the shooting, Mateen held hostages for three hours before security forces finally killed him.

Medical personnel who responded to the scene described the area as a "warzone", with blood and bullet-riddled bodies strewn everywhere. Some of those who survived had their extremities blown off.

Although local officials have urged the public to wait for the official investigation before jumping to conclusions, the Federal Bureau of Investigation (FBI) is treating the incident as an act of terrorism, the Washington Post reported.

According to the latest information, Mateen-an American citizen of Afghan descent who worked as a security officer for a large, private firm in Orlando-had been investigated by the FBI in 2013 and 2014 but was not deemed a threat. His ex-wife and family members described him as "not particularly religious" but had anger management issues.