Why Did Las Vegas Shooter Stephen Paddock Gun Down 58 Country Music Fans? FBI Agent Reveals When We'll Know

We likey won't find out what motivated Stephen Paddock to shoot dead 58 country music fans from the window of a Las Vegas hotel room—the deadliest mass shooting in modern U.S. history—for at least another nine months, if ever, the FBI agent in charge of probing the case reportedly revealed on Wednesday.

In an interview with the Las Vegas Review-Journal, Special Agent Aaron Rouse said the FBI is planning to release a report on the shooting just before the first anniversary of the massacre on October 1 that will center on why Paddock gunned down attendees of the Route 91 Harvest festival from his Mandalay Bay hotel suite. He committed suicide at the scene.

"Ours is focusing on large part on the why. Okay? Which is what everybody wants to know," Rouse told the newspaper.

He said the schedule was relatively quick for the FBI.

"Now that's a long time for some people, but speaking for the FBI, that's light speed, all right?"

Until that point, the FBI is not planning to release any details about the motive for the shooting, Rouse said.

So far, the FBI has interviewed more than 400 people across the world who had some sort of connection to 64-year-old Paddock, according to Rouse.

He told the Review-Journal his team is "learning as much as we possibly can" about what motivated Paddock, adding that "various psychological and sociological" experts have been called in to work on the case.

It was unclear if the FBI had yet zeroed in on a motive for the slaughter that left more than 500 people injured.

The Islamic State militant group (ISIS) initially claimed responsibility for the shooting, but Paddock's family, the FBI, and U.S. officials hesitated to believe that was the case.

And now Rouse said evidence has not yet shown that Paddock committed the shooting as part of an affiliation or ideology.

He also said that agents have so far concluded that he didn't have any co-conspirator, debunking original suspicions that Paddock's girlfriend might have had something to do with the shooting since he used her identification to secure his hotel room.

"I believe that there is one person and one person alone to blame for what happened on One October, and that is Stephen Paddock," Rouse told the Review-Journal.

The FBI has brought in 400 specialists to help catalog evidence from the festival venue after investigators took 14 days to document everything, he said. It took investigators 13 days to document Paddock's 32nd-floor suite, he added, boasting that agents will be able to generate a clear picture of how events played out on the deadly night.

"We're going to have, I think, the best digital schematic of what happened and where it happened and how it happened that you can come up with," Rouse said.

Investigators still have 22,000 hours of surveillance and cell phone footage, and 250,000 photos to look though, the Review-Journal reported. They also have to comb through 40 terrabytes of digital data.

"We didn't leave anything uncovered," Rouse said.