ISIS claims of responsibility for the mass shooting in Las Vegas where 58 people were killed and more than 515 wounded, and said the attacker had converted to Islam a few months ago have been disputed by the FBI.
Stephen Craig Paddock, 64, a resident of nearby Mesquite, Nevada, opened fire on a country music festival taking place at Las Vegas Village from a room across the street in the Mandalay Bay Hotel just after 10pm on Sunday evening.
However, by Monday morning, FBI investigators had 'determined that there is NO connection between the Vegas shooter and ISIS or international terrorism,' according to NBC.
It came after the claim was disputed down by unnamed US officials, who said there is no evidence he was linked to ISIS. Paddock's family had earlier said he had no religious or political affiliations.
"The Las Vegas attack was carried out by a soldier of the Islamic State and he carried it out in response to calls to target states of the coalition,' the group's news agency Amaq said in reference to the U.S.-led coalition fighting the group in the Middle East.
"The Las Vegas attacker converted to Islam a few months ago,' Amaq added.
Two senior U.S. officials said shortly after ISIS's statement that there was no evidence that the shooter was tied to any international militant group.
One of the two U.S. officials discounted Islamic State's claim of responsibility and said there was reason to believe that the shooter had a history of psychological problems.
In addition, Clark County Sheriff Joseph Lombardo said investigations are still ongoing and police have not yet determined a motive.
Paddock was not believed to be connected to any militant group, Lombardo said.
In an exclusive interview with Dailymail.com, the shooter's family said he had no political or religious affiliation.
"He was just a guy. Something happened, he snapped or something,' his brother Eric Paddock said from his home in Orlando, Florida
"He's my brother, we don't have a very close relationship but we talk occasionally. There's no rhyme or reason here, it makes no sense".
"He has no political affiliation, no religious affiliation, as far as we know. This wasn't a terror attack".
Paddock lived just 90 minutes outside Las Vegas in the city of Mesquite, with 62-year-old Marilou Danley, an Australian citizen believed to be of Indonesian descent.
Eric Paddock said of Ms Danley: 'She has nothing to do with this, at least from my perspective.
Police said in a press conference early Monday that that they discovered in 'excess of 10 rifles' in the room, and that Paddock's death was the result of a self-inflicted gunshot wound.