Investigators said Friday that after five days of piecing together the story of Stephen Paddock, they remained at a loss for what may have motivated him to open fire from his Las Vegas hotel suite, gunning down 58 people at a country music festival and injuring hundreds more.

Police say they have looked into more than 1,000 leads. Authorities have delved into his Paddock’s gun purchases, computers and travel plans, spoken to his relatives and traced his actions leading up to the shooting.

What they lack, however, are answers explaining why a 64-year-old avid gambler meticulously planned and carried out out the deadliest mass shooting in modern American history.

“We do not still have a clear motive or reason why,” Kevin McMahill, undersheriff of the Las Vegas Metropolitan Police Department, said at a news briefing Friday.

McMahill said he was aware that since Sunday’s massacre, rumors and speculation had abounded in the absence of a confirmed motive.

“I get it,” he said. “We all want answers. We have looked at everything, literally, to include the suspect’s personal life, any political affiliation, his social behaviors, economic situation, and any potential radicalization that so many have claimed.”

Unlike many other mass killers who have unleashed bloodshed in America’s churches, colleges, nightclubs, workplaces, college towns or public spaces, Paddock – who killed himself before police stormed his room – left no clear sign authorities have identified so far. After previous mass shootings, there were bigoted screeds posted online, confessions to police, videotaped rants, histories of violent behavior or worrisome trails of arrest records and mental health consultations.

Here, instead, there is mystery. And while trying to solve that question, police have also sought to determine whether anyone knew about the attack, McMahill said.

Investigators were “very confident that there was not another shooter in that room,” McMahill said. But they were continuing to investigate “whether anybody else may have known about this incident before he carried it out.” McMahill said they had reviewed surveillance camera footage from the Mandalay Bay Resort and Casino and “not located any other person that we believe to be a suspect at this point.” He told CNN that Paddock brought 23 guns and thousands of rounds of ammunition to his hotel suite on multiple trips over several days.

It also remains unanswered whether Paddock intended to die in his hotel suite or had initially hoped to escape. Paddock fired at a security guard on Sunday night and, at some point before a SWAT team entered his suite, killed himself.

Police also still have no answer for why Paddock had brought tannerite, an explosive, in his car to the Mandalay Bay.

“I don’t know what he was going to do with all that tannerite,” McMahill said. “I wish I did.”

Among the many things authorities were exploring was Paddock’s medical status, which McMahill said was an “aspect of the investigation we’re keenly interested in.”

People who knew Paddock described him as anti-social, someone who went out of his way to avoid other human beings, but his girlfriend said she saw no indication that he was capable of such horror.

As the investigation has produced a web of clues, police also explored some of Paddock’s recent potential travels. Before ascending to the 32nd floor of a Las Vegas hotel and opening fire on 22,000 concertgoers far below, Paddock had booked space in two other hotels overlooking popular music festivals – one in Las Vegas last month and the other in Chicago a month earlier.

Investigators were unsure of the significance of the hotel bookings and are trying to determine if they were ominous signs of the horror to come or the meaningless actions of a man with the financial means to fly around the country.

Those in Paddock’s life said they had no inkling of what was to come. FBI agents interviewed Marilou Danley, Paddock’s girlfriend, hoping she could provide insight into the shooting, but she has said she knew nothing of his plans or potential for such violence.

Danley was out of the country during the shooting, and she said this was arranged by Paddock, saying that he bought her a plane ticket to the Philippines to visit relatives. Paddock then wired her a substantial sum of money, telling her to use it to buy a home, Danley said in a statement read by her attorney.

“I was grateful, but honestly, I was worried, that first, the unexpected trip home, and then the money, was a way of breaking up with me,” Danley said. “It never occurred to me in any way whatsoever that he was planning violence against anyone.”

In Nevada, the Clark County coroner on Thursday formally identified the 58 people killed in the massacre.

Their names and stories have already emerged, tales of people gunned down while next to their friends and relatives. Some threw their bodies over loved ones to protect them from the gunfire, while others died in the arms of their husbands and wives.

Of the 58 people killed during the massacre, 36 were women and 22 were men. The youngest victim, Bailey Schweitzer, was 20; the oldest, Pati Mestas, was 67.

The rampage also sent nearly 500 people to the hospital, many with gunshot wounds. Others were injured during the frenzied attempts to flee the carnage. More than two dozen of those still hospitalized as of Thursday remained in critical condition.

McMahill pledged that investigators hoped to learn answers. The FBI joined with the Las Vegas police pleaded for information, launching a public information campaign – using the slogan “Know Something, Say Something” – seeking information about Paddock.

“We are looking at every aspect from birth to death,” McMahill said.