Despite the persistent claims by the Islamic State that it was behind the worst mass shooting in U.S. history, the Clark County Sheriff's Office said again Friday it has no evidence of any connection between the killer, Stephen Paddock, and the Islamic terrorist organization.

In fact, a Sheriff's spokesman said Friday authorities remain unable to tie the shooter to any other person or organization and remain totally baffled on what may have motivated him.

Law enforcement is so devoid of answers, in fact, that the FBI has partnered with Clear Channels, a chain of radio broadcasters, on a project to seek the public's help in solving the mystery of who or what may have inspired Stephen Craig Paddock to gun down hundreds of country music fans at an outdoor concert on Oct. 1 in Las Vegas.

ISIS released an infographic Friday in the 100th issue of its weekly newspaper, al-Naba, which shows the Mandalay Bay Resort and Casino hotel draped in blood, and stated that Paddock, whom they call Abu Abdul Amriki, had converted to Islam six months ago. This was a bit more specific than a previous online post in which ISIS claimed Paddock had converted "months ago."

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Paddock's brother, Eric, has said in interviews he had not seen Stephen in about six months.

ISIS said Paddock had "avenged his brothers" and "may Allah accept him" into heaven.

As early as 2016 ISIS released detailed guidance on how to obtain guns in the US and named concerts as a prime target. That was followed by the bombing at the Ariana Grande concert in London in May that killed 22 people and injured at least 50.

Dr. Mark Christian, a former Muslim imam and expert on Wahabbist and Salafist Islamic teachings, said he believes ISIS is milking the Las Vegas massacre for all it's worth and will, in time, provide some type of evidence of its involvement, possibly a video.

"How would ISIS have known that U.S. investigators wouldn't find a different motive that would debunk their claim?" said Christian, founder and director of the Global Faith Institute.

For every day that the U.S. government fails to explain the shooter's motive, this gives ISIS's claim more credibility, he said.

No other competing narrative has yet been put forth by either local police or the FBI that would explain Paddock's actions.

Dumbfounded deputies again faced the media on Friday with no answers.

Kevin McMahill, undersheriff for Clark County, Nevada, said at the press briefing that investigators still have no idea what motivated Paddock to methodically accumulate 33 guns over a one-year period and use them to gun down hundreds of people at the Route 91 country music concert held outside the Mandalay Bay. He killed 58 people and wounded 489.

McMahill said police have not seen any video or note from Paddock that would explain his actions.

This after police have repeatedly said Paddock video-taped himself in the room the night of the attack.

"I'm not aware we recovered any such video," McMahill said in answer to a reporter's question.

There was a note found in the shooter's room that reportedly contained numbers, but apparently no suicide note or manifesto explaining his motives.

No second shooter?

The sheriff's spokesman also threw cold water on theories about a second shooter.

But he said authorities have not ruled out an accomplice helping Paddock.

"We're very confident there was not another shooter in that room," he said. "What I am not confident about is whether anyone else may have known about this incident before he carried it out."

Video from the hotel is being examined.

"We have reviewed video from many locations and have not identified any other suspect at this point," McMahill said.

He also debunked a report by NBC News Friday that another person entered Paddock's room while his car had left the garage.

Citing senior law enforcement officials involved in the investigation, NBC reported that investigators are puzzled by two discoveries: First, a charger was found that does not match any of the cellphones that belonged to the gunman, Stephen Paddock.

And second: Garage records show that during a period when Paddock's car left the hotel garage, one of his key cards was used to get into his room.

"We do not believe that happened," McMahill said. "I'm not aware of that information."

This would lead one to believe that either the FBI is not sharing all of its information with the Sheriff's Office or McMahill and others addressing the media have been deliberately kept out of the loop.

McMahill said "speculation" in the media has "not been helpful" to the investigation.

"We still do not have a clear motive or reason why. I can assure you we are aware of all aspects of this case, including the rumors and innuendo of the public, and I get it, we all want answers," McMahill said.

"We have looked at every aspect of his life…even potential radicalization. As everyone knows ISIS has claimed responsibility, a claim which today I can tell you we have no known nexus to. We have been down each one of these paths trying to determine, why? We will continue to investigate each and every one of these areas including tips that continue to come in. But we must remain focused on fact. To this time we have no credible information to report to you as to motivation. All the rumor and speculation has not been helpful to our investigation, in the past the motive has been made very clear by a social media post, a note, a telephone call that was made, but to date we don’t have any of those in this case. I wish we did."

About the explosive materials found in Paddock's vehicle, he said there remain many unanswered questions.

"Sorry to say I don't know what he planned to do with the Tannerite," McMahill said. "We found it in the condition it was and I can tell you it did not resemble an IED."

With regard to the shooter's medical status, he said it was something which "we are very interested and are still very interested in that."

"We are looking at every aspect from birth to death of the suspect in this case."

Case 'unlike any other'

Former secret service agent Dan Bongino said the case is unlike any other mass shooting he's seen.

"This case is really an enigma," he told Fox News' Neil Cavuto. "It doesn’t seem to make any sense. In my experience, you usually have two types of suspects in these cases, those radicalized by an ideology or those with some type of psychological disorder, and with this one neither seems to make sense. There's none of those pre-attack indicators. I don't think the FBI or local police have that much information on this case, either, because they're putting up billboards and asking for information. This is a very disturbing case."

Another angle that makes no sense to Bongino is the Tannerite found in Paddock's car.

"Tannerite is normally used for low-impact detonation, you would only use Tannerite to practice long-distance shooting to see where your round hit and detonate where it hit. It doesn't make sense why he would accumulate all those rounds and at his car, it's just another mystery, it doesn't make a lot of sense."

So as information about the shooter continues to accumulate, his motive continues to elude authorities.

New revelations Friday included reports that Paddock made use of free prostitutes offered to him by the casino, while his girlfriend said she felt jittery around him. Marilou Danley also told the FBI that Paddock woke up at night screaming and moaning as if he was being tormented by mental anguish.

Investigators are also examining his finances. IRS records show Paddock was a successful gambler, earning at least $5 million in 2015 from gambling and real estate deals.

Senior law enforcement officials said Paddock, 64, had researched possible attack locations at concerts n Boston and Chicago, including the Lollapalooza festival in Chicago in August.

Paddock’s brother, Eric, claimed he had “no religious affiliation, no political affiliation” or history of mental illness.