Stephen Paddock reportedly secured a room overlooking Chicago's Grant Park while the festival was being held in August.
The gunman who carried out the deadliest mass shooting in modern American history may have plotted a similar attack at another music festival that was attended by President Obama's daughter Malia two months ago.
Read: Vegas Gunman May Have Been Plotting to Strike Another Vegas Music Festival a Week Earlier
More than 400,000 people came out for August’s annual Lollapalooza festival in Chicago's historic Grant Park, which featured performances by The Killers, Chance the Rapper, Lorde, Arcade Fire, Justice and Liam Gallagher.
Among the revelers was 19-year-old Malia Obama, who also attended the 2016 event.
A man believed to be Stephen Paddock booked two rooms at the city's famed Blackstone Hotel for the week that Lollapalooza was being held, but never checked in.
The windows of the Blackstone would have given Paddock a direct line of fire to crowds at the concert.
Investigators additionally believe he also scouted Boston's Fenway Park via a Google search.
Meanwhile, police say they are looking for a possible accomplice to Paddock in the Vegas massacre.
“It's troublesome this individual was able to move this amount of gear inside the hotel room unassisted, Clerk County Sheriff Joe Lombardo said. “You got to make the assumption he had to have some help at some point.”
Read: Vegas Shooter Hid Hotel Arsenal by Hanging 'Do Not Disturb' Sign on Door for 3 Days
Paddock's purported room service receipt at the Mandalay Bay reveals he ordered an Angus double burger and a bagel with cream cheese, potato soup, mineral water and two Pepsi drinks.
The receipt indicated that the order was for two guests.
The Las Vegas Review Journal newspaper is reporting that two fuel tanks at McCarren International Airport were shot, but the bullets did not pierce the tanks.
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