The top FBI official in Nevada said his agency's report about the shooting last year that killed 58 people and injured hundreds on the Las Vegas Strip is in the finishing stages but won't be released until after the Oct. 1 anniversary.

Special Agent in Charge Aaron Rouse said in a radio interview aired Monday that he doesn't expect the report, which includes information collected from nearly 1,000 agents who contributed to the investigation in the U.S. and 25 countries, will pinpoint a motive behind the deadliest mass shooting in the nation's modern history.

"I want it right. I don't need it fast," Rouse told National Public Radio station KNPR in Las Vegas. He said the report will focus on "how this happened, can it happen again, what are we going to try and stop it the next time?'"

Authorities are confident Stephen Paddock was the only shooter and that Paddock killed himself before police arrived, Rouse said without using Paddock's name. The FBI official said the attack did not involve a broader conspiracy.

Rouse had said in January that an FBI report would probably be released near the one-year anniversary of the shooting. He now says it will probably be by the end of the year.

"Will you have a definitive why? I can't say that for sure," Rouse said. "What I can say is that absent talking to the person who committed this heinous act, I believe that we'll have a great deal of information — enough for people to understand to the extent possible why this happened."

A separate report by Las Vegas police could come within weeks. Clark County Sheriff Joe Lombardo, the elected head of the Las Vegas Metropolitan Police Department, had said he expected the report in July. A department spokesman said recently the document is not yet complete.

Meanwhile, police have been releasing incident reports, witness accounts, officer body-camera recordings and casino and streetscape surveillance video under a court order in a public records lawsuit by media including The Associated Press.

The material was collected after Paddock opened fire from an upper-floor suite at the high-rise Mandalay Bay resort into a concert crowd of 22,000 at an outdoor venue at the Route 91 Harvest Festival across Las Vegas Boulevard.

Police who used explosives to enter the room found Paddock dead inside. The Clark County coroner determined that he shot himself.

Rouse said lessons learned in the investigation are being used to improve security at outdoor events nationwide, and that he has briefed law enforcement and security officials on ways to better assess risks at open-air venues.