After three months of investigation, police have learned more about Las Vegas gunman Stephen Paddock: He was a high-stakes gambler on a losing streak, obsessed with cleanliness, possibly bipolar and was having difficulties with his live-in girlfriend.

But hundreds of interviews and thousands of pieces of evidence have not answered the key question: Why did Paddock open fire from his high-rise hotel suite, killing 58 people and injuring more than 800 others in the deadliest shooting in modern US history?

Clark County Sheriff Joe Lombardo released a preliminary report yesterday on the October 1 attack on an outdoor concert staged from a room at the Mandalay Bay casino-hotel and said he did not expect criminal charges to be filed against Paddock’s girlfriend, Marilou Danley, who had been named as the only person of interest in the case.

Investigators believe Paddock acted alone and did not leave a suicide note or manifesto before he was found dead in the room.

Weeks before the shooting, the couple stayed at Mandalay Bay together but Paddock was acting strangely, Danley told investigators.

She remembered him constantly looking out the windows overlooking an area where the concert would be held the next month. He moved from window to window to see the site from different angles, the report said.

Paddock had become “distant” in the year before the shooting and their relationship was no longer intimate, Danley said during an interview with investigators. She described him as germophobic and said he had strong reactions to smells.

Paddock, who fatally shot himself in his hotel room, had told friends and relatives that he always felt ill, in pain and fatigued.

His doctor thought he may have had bipolar disorder but told police that Paddock refused to discuss the possibility, the report said. The doctor offered him antidepressants, but Paddock accepted only a prescription for anxiety medication.

Paddock was fearful of medication and often refused to take it, the doctor told investigators.

The 64-year-old retired accountant and real estate investor had lost a “significant amount of wealth” since September 2015, which led to “bouts of depression,” the sheriff has said. Paddock had paid off his gambling debts before the shooting, according to the report.

Danley was in the Philippines at the time of the shooting. In the days before the attack, Paddock sent her a USD 100,000 wire transfer. She has said she found that odd and thought he might have been breaking up with her when he sent her the money and told her to use it to buy a home for her family there.

During an interview with the FBI after she returned from the Philippines, Danley volunteered that investigators would find her fingerprints on bullets used during the attack because she would sometimes help Paddock load high-volume ammunition magazines, according to FBI warrant documents.

Investigators found 23 rifles and a handgun in his hotel suite and more than a dozen of the rifles were fitted with “bump stock” devices that allowed rapid-fire shooting similar to fully automatic weapons. Dozens of guns were strewn around the room, some left inside a bassinet.

In their report, police released never-before-seen photos from inside the hotel suite, including one shot through a broken window, showing the concert venue still littered with personal belongings left when thousands ran to escape the hail of bullets raining from above.

Paddock fired more than 1,100 bullets, mostly from two windows on the 32nd floor of the hotel, into a crowd of 22,000 people attending the Route 91 Harvest Festival music below, Lombardo has said.

That includes about 200 shots fired through his hotel room door into a hallway where an unarmed hotel security guard was wounded in the leg and a maintenance engineer took cover.

Prior to the attack, Paddock had researched SWAT tactics and searched online for other potential public targets, including in Chicago, Boston and Santa Monica, California, the sheriff said. His research also sought the number of attendees at other concerts in Las Vegas and the size of the crowds at Santa Monica’s beach. Among his searches was “do police use explosives,” the report said.