(CNN)It took about an hour and 15 minutes from the moment Stephen Paddock opened fire on Route 91 Harvest Festival concertgoers Sunday to the time a SWAT team burst through the door of his Las Vegas hotel room.
The cold, calculating timeline of the Las Vegas gunman
But based on his activities leading up to the concert, authorities say Paddock may have been planning the shooting for months.
This is how events unfolded, according to law enforcement. All times are Pacific.
Oct. 2016-Sept. 2017
Paddock purchases 33 firearms, mostly rifles, over the course of an 11-month period, according to a spokesperson for the Bureau of Alcohol, Tobacco, Firearms and Explosives.
Investigators are looking into whether something occurred in October 2016 that compelled him to begin purchasing weapons.
A person using the name Stephen Paddock reserves a room at the Blackstone Hotel in Chicago in August during the Lollapalooza Music Festival, according to Emmy Carragher, a spokeswoman for Wagstaff Worldwide Media, which represents this Marriott hotel.
Lollapalooza was held in Grant Park in Chicago from August 3-6. The Blackstone Hotel overlooks the park.
That person never checked into the hotel, Carragher told CNN. It's not immediately clear whether the individual is, in fact, Las Vegas gunman Stephen C. Paddock.
Hurricane Irma hits Florida. Stephen Paddock texts his brother Eric and his mother, who live in Florida, to ask how his mother is doing and whether they have power, according to Eric Paddock. Stephen Paddock talks to his mother on the phone and sends her a walker because she's having trouble walking, Eric Paddock tells CNN.
After leaving the US, Paddock's girlfriend, Marilou Danley, flies from Tokyo, Japan, to the Philippines. She says Paddock bought her the airline tickets and then wired her money so she could buy herself a house there. One of her sisters says she believes Paddock sent Danley away so she wouldn't interfere with his plans.
Marilou Danley, traveling on her Australian passport, flies from the Philippines to Hong Kong.
Stephen Paddock rents a room at a condominium complex in downtown Las Vegas at the same time as the Life is Beautiful music festival, which featured performances from Chance the Rapper, Muse and Lorde.
"Was he doing pre-surveillance?" Sheriff Joseph Lombardo of the Las Vegas Metropolitan Police Department asked. "We don't know yet, this is all conjecture at this point."
Marilou Danley flies from Hong Kong back to the Philippines.
Paddock checks into a suite on the 32nd floor of the Mandalay Bay Resort and Casino with uninterrupted views of the Las Vegas Strip and the festival grounds across the street.
Sept. 28-Oct. 1
Over the course of several days, Paddock brings in excess of 10 suitcases up to his suite, Sheriff Lombardo says. Housekeepers visited the suite and did not see anything amiss, Nevada Rep. Dina Titus told CNN.
Paddock sets up at least 23 weapons inside his hotel room, including multiple rifles, some of which had scopes. He also attaches 12 "bump-fire stocks" -- devices that enable shooters to fire bullets at a faster rate -- on the guns.
Paddock sets up cameras inside his hotel suite, in the hallway and in his door's peephole, all of which may have been used to watch for people approaching his room, Lombardo says.
The Route 91 Harvest Festival, a three-day country music concert, kicks off at the Las Vegas Village, a venue across the Strip from the Luxor hotel and the Mandalay Bay Resort and Casino.
Country music star Jason Aldean begins his set as the final musical act of the festival.
Jesus Campos, a Mandalay Bay Resort and Casino security guard, is shot in the leg while investigating an alarm in a different room on the 32nd floor.
Paddock smashes out two windows of his suite with a hammer, then opens fire at the 22,000 concertgoers below. The shots are caught on closed-circuit television from the concert venue. Concertgoers, confused at first, soon scatter in panic.
Two Las Vegas police officers make it to the 31st floor of the Mandalay Bay after working their way up the building. One radios in: "I'm inside the Mandalay Bay on the 31st floor, I can hear automatic fire coming from one floor ahead... one floor above us."
Paddock fires his final shots, which are recorded on an officer's bodycam.
The first two officers arrive on Paddock's floor.
Eight more officers arrive on the 32nd floor. Not hearing gunfire, they move down the hall, clearing rooms along the way in case the shooter has barricaded himself.
The officers arrive in the stairwell nearest the suite at the north end of the hall. Noting two cameras set up on a room service cart, they pull back to wait for a SWAT team.
SWAT officers use an explosive to breach the door to Paddock's suite and discover him dead on the floor, apparently of a self-inflicted gunshot wound. Officers note the door to one of the suite's bedrooms is closed.
The SWAT team uses another charge to gain entry to the bedroom and discover no one else is there. An officer radios that the suspect is down.
This story has been updated with the latest information from police regarding the timeline of the shooting.