Omar Mateen, the gunman who killed nearly 49 people at a gay nightclub in Orlando, Florida, pledged allegiance to the Islamic State (IS) on Facebook message which he posted moments before the worst mass shooting in the US. \u201cAmerica and Russia stop bombing the Islamic state..I pledge my alliance to (IS leader) Abu Bakr al Baghdadi ..may Allah accept me,\u201d Mateen posted. \u201cThe real muslims will never accept the filthy ways of the west\u201d and \u201cYou kill innocent women and children by doing us airstrikes..now taste the Islamic state vengeance.\u201d According to the report, Mateen also declared allegiance to IS and al-Baghdadi in 911 calls he made during the attack, CBS News reported on Thursday. Also Read:\u00a0Orlando Shooting: Details emerge about nightclub shooter's wife A US Federal Bureau of Investigation (FBI) official said the massacre at the Pulse nightclub was both hate crime and an act of terror. "This was an act of violence, born out of hate, that inflicted terror on an entire community," said Ron Hopper, special FBI agent in charge of the case. "So I would call it a hate crime. I would call it terrorism. It's both," Xinhua news agency quoted Hopper as saying. The US authorities were also considering filing criminal charges against Mateen's wife, Noor Salman, for failing to inform the FBI what she knew before the attack. Salman, has told the FBI that she drove Mateen, 29, to the Pulse nightclub on a prior occasion but that she tried to talk him out of the deadliest mass shooting in modern US history, officials told NBC News. Several officials familiar with what she has told the FBI said she was with him when he bought ammunition and a holster. She also once drove him to the nightclub because he wanted to see it in advance, the officials said. The couple has been married since 2011. They have a three-year-old son. The FBI is investigating reports that Mateen made several visits to the Pulse nightclub and made contact with other men on gay dating apps. President Barack Obama was scheduled to travel to the scene of the attack in Orlando on Thursday.