The Las Vegas gunman meticulously planned how to carry out the worst mass shooting in modern U.S. history, researching SWAT tactics, renting other hotel rooms overlooking outdoor concerts and investigating potential targets in at least four cities, authorities said Friday.
But months after Stephen Paddock killed 58 people and wounded more than 800 others with a barrage of bullets from the Mandalay Bay casino-hotel, investigators still have not answered the key question: Why did he do it?
On Friday, Clark County Sheriff Joe Lombardo released a preliminary report on the Oct. 1 attack and said he did not expect criminal charges to be filed against Paddock's girlfriend, Marilou Danley, who had been previously called a person of interest in the case. Investigators also found that Paddock had possessed child pornography, Lombardo said.
During an interview with investigators, Danley said Paddock had become "distant" in the year before the shooting and their relationship was no longer intimate.
When they stayed at the Mandalay Bay together in September 2017, Paddock acted strangely, she told investigators. She remembered him constantly looking out the windows overlooking an area where the concert would be held the next month, moving from window to window to see the site from different angles, the report said.
Paddock's online searches before the shooting included research into SWAT tactics and consideration of other potential public targets, including in Chicago, Boston and Santa Monica, California, the sheriff said.
His research included the number of attendees at other concerts in Las Vegas and the size of the crowds at Santa Monica's beach.
In-depth news coverage of the Greater Boston Area.
Paddock, a 64-year-old retired accountant and multimillionaire real estate investor, killed himself with a gunshot to the mouth before police reached him.
Authorities have said they found no link to international terrorism. They believe Paddock meticulously prepared his plan to fire assault-style weapons from the 32nd floor of the Mandalay Bay hotel into a crowd of 22,000 people attending the Route 91 Harvest Festival music below.
Paddock fired more than 1,100 bullets, mostly from two windows, 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.
Several bullets hit fuel storage tanks at nearby McCarran International Airport that did not explode. Authorities reported finding about 4,000 unused bullets in Paddock's two-room suite, including incendiary rounds that Lombardo said were not used.
Investigators found 23 guns in the rooms, including 12 rifles that a federal Bureau of Alcohol, Tobacco and Firearms official said were fitted with "bump stock" devices that allowed rapid-fire shooting similar to fully automatic weapons.
Danley was in the Philippines at the time of the attack.
Lombardo and Aaron Rouse, FBI agent in charge in Las Vegas, had described Danley as a person of interest in the investigation but not a suspect. She was questioned by the FBI when she arrived in Los Angeles from overseas, and was described as cooperating with investigators.
However, a document filed Oct. 6 and recently unsealed by a federal judge in Las Vegas said the FBI considered Danley "the most likely person who aided or abetted Stephen Paddock."
Questions have been raised about Danley's receipt in the Philippines of a $10,000 wire transfer from Paddock just days before the shooting.
FBI warrant documents also showed that Danley told investigators that they would find her fingerprints on bullets used during the attack because she would sometimes help Paddock load high-volume ammunition magazines.