Police say they're increasing security for Sunday's Chicago Marathon after a gunman opened fire on an outdoor music festival in Las Vegas earlier this week, killing 59 people.
Before the deadliest mass shooting in modern US history, the Las Vegas gunman checked into the Mandalay Bay Hotel, requesting an upper-floor room with a view of the Route 91 Harvest Music Festival, according to a person who has seen hotel records turned over to investigators.
Both rooms had a checkout date of August 6, corresponding with the final day of the music festival that drew tens of thousands of concert-goers to Grant Park alongside Lake Michigan.
He booked a second room for an August 3 arrival.
Stephen Paddock is the man responsible for America's worst ever mass shooting. Lombardo said at a news conference.
Three days later, he shot into the crowd of about 22,000 concertgoers during the performance of the Route 91 Harvest festival's headliner, Jason Aldean.
His girlfriend, Marilou Danley, 62, said in a statement that she had no idea what he was planning or why.
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Investigators trying to determine what triggered the massacre say Paddock's plans were meticulous.
"When we did see he was gambling, we did not see another individual appearing there".
The official was not authorized to discuss the case publicly and spoke on condition of anonymity after being briefed on the investigation.
The FBI's Aaron Rouse said they were aware Paddock was gambling before the shooting. "We're the city of big shoulders, we put on big events.and people enjoy them.this is where Chicago can shine and is capable", said Emanuel.
Investigators have zeroed in on a weapon-buying binge Paddock went on in the year before the attack. He had no known criminal record and nearly no close friends or social media presence.
Ms Danley, who returned to the U.S. late Tuesday from a family visit to the Philippines, is regarded by investigators as a "person of interest".