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(CNN) —  

In the two days before Omar Mateen terrorized the Pulse nightclub, he bought plane tickets to California for his wife, his child and himself – for a July trip he would never take.

He worked his normal shift as a security guard – giving no clues he was about to commit the worst mass shooting in U.S. history.

He spent hours at the Disney Springs shopping complex, by himself.

And he went to the Pulse nightclub before midnight on June 11, only to leave and then return two hours later and kill 49 people.

So what did he do during those two hours? And what did he do in the months, weeks and days leading up to the attack?

More clues are emerging, but some gaps remain. And crucial details such as what drove Mateen to kill may never be fully known.

“I cannot tell you definitively that we will ever narrow it down to one motivation,” U.S. Attorney General Loretta Lynch said.

This is what we know about the attacker’s movements, from his first interviews with the FBI in 2014 to the attack.

2014: FBI questions Mateen; mosque member tips feds off

  • The FBI interviews Mateen about possible connections with Moner Mohammad Abu-Salha, a Florida man who became the first known American suicide bomber in Syria. The two men frequented the same mosque.
  • Mohammed Malik, another man from Mateen’s mosque, notifies the FBI that Mateen spoke of Anwar al-Awlaki – the American-born Muslim scholar and cleric who acted as a spokesman for al Qaeda in the Arabian Peninsula. Mateen also watched al-Awlaki’s videos, Malik said.

Months before the attack: Financial preparations

  • Mateen adds the name of his wife, Noor Salman, to his life insurance policy and made sure she had access to his bank accounts, two law enforcement officials said.
  • The gunman transferred his share of the home in which his sister and brother-in-law live to them for just $10.
  • Mateen also bought his wife an expensive piece of jewelry, the sources said.

April 26, 2016: Possible surveillance trip at Disney World

  • Mateen visits Disney World with his wife, and Disney security officials believe he was conducting surveillance, a law enforcement official told CNN.
  • Authorities are investigating whether Salman, his wife, might have known in advance about her husband’s plans for the attack.

Late April or early May 2016: Trying to buy body armor

  • Mateen goes to Lotus Gunworks in Jensen Beach, Florida, and tries to buy body armor and 1,000 rounds of ammunition.
  • A store employee tells Mateen the shop doesn’t sell the body armor or bulk ammo that Mateen was looking for, store owner Robert Abell said.

June 1 to June 6: Surveillance trips and firearm purchases

  • Mateen visits Pulse and the Disney Springs shopping complex between June 1 and June 6, a law enforcement analyst said. The visits coincide with Gay Days 2016 in Orlando. Authorities believe Mateen was conducting surveillance.
  • After clearing a background check, he legally purchases a Sig Sauer MCX assault-style rifle and a Glock 9mm semiautomatic pistol.

June 10: Two days before the attack

June 11: The day before the massacre

  • He finished his regular shift as a security guard at PGA Village in the mid-afternoon.
  • Mateen makes one more trip to Disney Springs. It’s not clear why.
  • He leaves his house angry, carrying a bag of guns, his wife tells investigators. His home in Fort Pierce is about a two-hour drive from Orlando.
  • Salman begs her husband not to leave, grabbing him by the arm, she told investigators. Salman later said she didn’t know he was planning the attack.
  • Mateen goes to Pulse nightclub, pays the entrance fee, gets a wristband, enters the club and later leaves. Investigators say he may have been scoping out the club’s security.
  • Investigators are trying to find out what Mateen did in the two hours after his Saturday night visit to Pulse and his Sunday morning massacre.

June 12, 1:58 a.m. ET: The first gunshots

  • Mateen fires his first shots in the Pulse nightclub, which is packed with more than 300 people.

June 12, before and during the attack: Facebook posts

  • Mateen vented on Facebook before and during the massacre. “America and Russia stop bombing the Islamic state,” the gunman wrote, according to the chairman of the Senate Homeland Security Committee. “You kill innocent women and children by doing us airstrikes … now taste the Islamic state vengeance.”
  • Then, in his final post, an ominous warning: ”In the next few days you will see attacks from the Islamic state in the usa.”

June 12: The final texts and calls

  • Mateen texted his wife at 4 a.m., two hours after the carnage started, asking her if she’s heard the news about the shooting. At one point, Salman told Mateen that she loved him.
  • During the rampage, Mateen also calls 911 and pledges his allegiance to ISIS. He calls CNN affiliate News 13 in Orlando to say he’s the shooter, adding, “I did it for ISIS. I did it for the Islamic State.”

June 12, 5:53 a.m. ET: Mateen is dead

  • Orlando police tweet that the gunman is dead.

CNN’s Drew Griffin, Brian Todd, Evan Perez, Shimon Prokupecz, Pamela Brown and Dugald McConnell contributed to this report.