After nearly 16 months, the agency said it could not determine why gunman Stephen Paddock killed 58 people and injured hundreds of others in October 2017.

This October 2017 photo released by the Las Vegas Metropolitan Police Department Force Investigation Team Report shows the view of Las Vegas Village from Mandalay Bay's room 32-135, part of the evidence images included on a preliminary report showing the interior of Stephen Paddock's 32nd-floor room at Mandalay Bay in Las Vegas. (Las Vegas Metropolitan Police Department via AP)

People assist a wounded woman at Tropicana Las Vegas after the mass shooting on Oct. 1, 2017. Chase Stevens Las Vegas Review-Journal @csstevensphoto

A wounded person is tended to as Las Vegas police respond after the mass shooting on Oct. 1, 2017. Chase Stevens Las Vegas Review-Journal @csstevensphoto

Las Vegas police patrol in a convention center area during lockdown on Oct. 2, 2017, at Tropicana Las Vegas. Chase Stevens Las Vegas Review-Journal @csstevensphoto

The FBI investigates atop the Route 91 Harvest main stage at the Las Vegas Village festival grounds on Oct. 11, 2017. Richard Brian Las Vegas Review-Journal @vegasphotograph

A sign near a memorial at Las Vegas Boulevard and Sahara Avenue in Las Vegas during the early hours of Tuesday, Oct. 3, 2017. Chase Stevens Las Vegas Review-Journal @csstevensphoto

Mike and Jessica Yerkey of Ramona, Calif., pause at a memorial at Las Vegas Boulevard and Sahara Avenue in Las Vegas during the early hours of Tuesday, Oct. 3, 2017. Chase Stevens Las Vegas Review-Journal @csstevensphoto

Participants take part in a candlelight vigil on Oct. 2, 2017, at the intersection of Las Vegas Boulevard South and West Sunset Road. Richard Brian Las Vegas Review-Journal @vegasphotograph mass shooting

People take in a memorial at Las Vegas Boulevard and Sahara Avenue in Las Vegas during the early hours of Oct. 3, 2017. Chase Stevens Las Vegas Review-Journal @csstevensphoto

Broken windows at Mandalay Bay in Las Vegas on Oct. 2, 2017, after a shooting left 58 concertgoers dead. Richard Brian Las Vegas Review-Journal @VegasPhotograph

A panel of experts with access to troves of evidence failed to determine why a gunman carried out the Route 91 Harvest festival attack, the FBI announced Tuesday.

The revelation smothered what many survivors saw as the last chance to better understand why the worst mass shooting in modern American history unfolded at a country music festival on the Strip.

In a three-page summary report, the agency also reiterated that gunman Stephen Paddock, 64, acted alone.

“Throughout his life, Paddock went to great lengths to keep his thoughts private, and that extended to his final thinking about this mass murder,” the report stated. “Active shooters rarely have a singular motive or reason for engaging in a mass homicide.”

The newly released report marks the first time the FBI has released any documentation from its investigation of the 10-minute attack, which left 58 concertgoers dead and more than 800 injured.

In a list of 10 key findings, it paints a picture of a largely apathetic man, declining in physical and mental health as he aged, who may have seen the attack as a way to attain infamy.

A spokeswoman for the Las Vegas FBI said Tuesday no other reports related to the investigation will be released. In the weeks after the Las Vegas attack, the FBI released more than 1,500 pages of documents related to the 2012 Sandy Hook Elementary School massacre investigation in Newtown, Connecticut.

“Fifteen months later, and we get a three-page report with little to nothing in it that we didn’t already know?” Stacie Armentrout, co-founder of a local Route 91 survivors group, told the Las Vegas Review-Journal on Tuesday.

Las Vegas police released a separate, 187-page investigative report in August with similar findings. Armentrout had hoped the FBI report would provide answers that the police report could not, specifically for the question of motive.

“Each individual person now has to figure out how to come to grips with that,” she said. “Now we have to figure out how to move forward without that.”

No suicide note

The Oct. 1, 2017, attack ended when Paddock, who was positioned inside a Mandalay Bay hotel suite across from the festival, shot himself with a revolver.

Police have said he fired more than 1,000 rounds that night, using about a dozen different rifles equipped with bump stocks, which replicate automatic fire.

Investigators found no suicide note, video, manifesto or other form of explanation regarding the attack. The agency also found no evidence that Paddock was motivated by any ideological or political beliefs.

Instead, they determined that Paddock wanted to die by his own hands, possibly seeing suicide as an act of control in a life that seemed to keep spiraling into decline as he grew older: His financial status fell, his level of functioning slowly diminished, and he grew increasingly distressed at his inability to remedy those issues, the report said.

“It would be nice to have answers,” said Las Vegas resident Mynda Smith, who lost her 46-year-old sister, Neysa Tonks, in the attack.

Smith and her family don’t blame the FBI for not being able to reach any real conclusions, she said. That’s just something else the gunman took when he did what he did.

Mostly, she’s glad Paddock is dead so he can’t inflict any more evil on the world.

“We’d much rather he be gone and be answerless,” she said, “than for him to be here and to have all the answers.”

Desire for ‘infamy’

The experts concluded that Paddock’s desire to die by suicide “was compounded by his desire to attain a certain degree of infamy” through a mass casualty attack.

In that aspect, the report noted, he may have been influenced by his father, a convicted bank robber who escaped from federal prison in 1968 and landed on the FBI’s Ten Most Wanted Fugitives list. He was arrested nearly a decade later, largely absent from Paddock’s life, and died in 1998.

“Paddock’s father created a facade to mask his true criminal identity and hide his diagnosed psychopathic history, and in so doing ultimately achieved significant criminal notoriety,” according to the report.

Paddock also had no known grievance with Mandalay Bay, Route 91 or anyone he killed.

Rather, investigators believe that he picked the resort because it was tactically “advantageous” and that he decided to initiate the attack during the festival because he knew the crowd below would be densely packed with “unsuspecting and vulnerable people.”

Throughout his life, Paddock was known to exhibit minimal empathy, primarily viewing others “through a transactional lens of costs and benefits,” the report noted.

“Paddock’s decision to murder people while they were being entertained was consistent with his personality,” the report stated. “He had a history of exploiting others through manipulation and duplicity, sometimes resulting in a cruel deprivation of their expectations without warning.”

On the night of the attack, police found 50 pounds of the explosive compound Tannerite in Paddock’s car, parked in the hotel’s valet lot. He also sealed the stairwell door just outside his suite with an “L” bracket, which responding officers broke by hand before .

But experts believe that Paddock never intended to escape, pointing to the many cameras he set up to ensure he could kill himself at a time of his choosing.

If anything, experts believe he may have started the attack early, spotting on those cameras an unsuspecting Jesus Campos, the Mandalay Bay security guard who was checking on a different matter in the 32nd-floor hallway minutes before Paddock began firing on the festival crowd below.

After at least one volley of gunfire, Paddock fired into the hallway, injuring Campos in the left calf.

Behavioral Analysis Unit

The report was compiled over the course of a year by a panel of experts convened by the FBI’s Behavioral Analysis Unit. The experts came from such fields as threat assessment, cyber behavioral analysis, child sexual exploitation, psychology, psychiatry and law.

Findings from the panel were ready as early as November 2018, and according to the agency, they were initially shared with Las Vegas police. It is unclear why the report was not released to the public until Tuesday.

Aaron Rouse, special agent in charge of the FBI’s Las Vegas office, told the Review-Journal in December 2017 that Paddock’s motive was something “everybody wants to know.”

But, he added, “we may never know.”

The agency denied a request to speak with Rouse on Tuesday. Clark County Sheriff Joe Lombardo also denied an interview request.

Shawna Bartlett, a Route 91 survivor who lives in Missouri, told the Review-Journal on Tuesday that she was not interested in knowing why the attack was carried out.

“I can’t speak for others, but I can say that I think the general opinion is that nobody ever expected to get a motive,” she said, “and that even if we did, it wouldn’t change anything.”

Knowing why might make her even angrier, she said.

“What instead needs to be glorified is the love, the positivity and the good things that have come from this,” she said, her voice breaking. “That in itself is a stronger story than why he did what he did.”

Contact Rachel Crosby at rcrosby@reviewjournal.com or 702-477-3801. Follow @rachelacrosby on Twitter. Review-Journal staff writers Rio Lacanlale and Henry Brean contributed to this report.