"[38] At 2:22 a.m., Mateen placed a 911 call, during which he mentioned the Boston Marathon bombers—Tamerlan and Dzhokhar Tsarnaev—as his "homeboys" and made a reference to Moner Mohammad Abu Salha, an American citizen who died in a suicide bombing in Syria in 2014.

[21][39][40] Mateen said he was inspired by Abu Salha's death for the Al-Nusra Front targeting Syrian government troops (a mutual enemy of the two Salafist groups, despite their history of violence with each other), and swore allegiance[41] to IS leader al-Baghdadi.

[21][54] At approximately 4:29 a.m., Mateen told negotiators that he planned to strap explosive vests, similar to those used in the November 2015 Paris attacks, to four hostages, strategically place them in different corners of the building, and detonate them in 15 minutes.

'"[54] During the siege, Mateen made Internet searches on the shooting, while police dispatched a tactical robot to discreetly enter the restroom and allow them to communicate with hostages via two-way audio.

[1] The FBI reported that no shots were heard between the time Mateen stopped exchanging gunfire with the first responders and 5:02 a.m., when Orlando police began breaching the building's wall.

[54] Just before the breach, Mateen entered a women's bathroom where the hostages were hiding and opened fire, killing a man who sacrificed his life to save the woman behind him and at least one other, according to witnesses.

[27][80][81] The names and ages of the victims killed were confirmed by the City of Orlando after their next of kin had been notified:[82][83] Autopsies of the 49 dead were completed by the Orange County Medical Examiner's Office by June 14,[84] and their results were released in early August.

[126] In September 2016, an imam for a mosque in Kissimmee released video footage showing what appeared to be Mateen on June 8, four days before the shooting, praying for about ten minutes.

[127] In the hours before the shooting, Mateen used several Facebook accounts to write posts vowing vengeance for American airstrikes in Iraq and Syria and to search for content related to terrorism.

These posts, since deleted, were recovered and included in an open letter[128] by Senate Homeland Security Chairman Ron Johnson to Facebook CEO Mark Zuckerberg seeking further information about Mateen's use of the site.

[139][140] Law enforcement sources said the FBI found no photographs, text messages, smartphone apps, pornography, or cell tower location data to suggest Mateen lived a gay life, closeted or otherwise.

[150][151] Following the shooting, many business venues in the United States, such as shopping malls, movie theaters, bars, and concert halls, reexamined their security procedures.

[158] On September 10, the Florida Department of Agriculture and Consumer Services fined G4S Secure Solutions $151,400 for providing inaccurate psychological testing information on more than 1,500 forms over a ten-year period, which allowed employees to carry firearms.

Doctors have emphasized the importance for school faculty members to stay calm and assess injuries, but also discouraged the use of more invasive emergency procedures such as removing a bullet.

"[162] The OVA, through its Victim Assistance Rapid Deployment Team and Crisis Response Canines, also provided help to responders of the shooting in the days following June 12.

Despite expressions of frustration and disapproval by a number of gay and bisexual men, and LGBT activists across the country and a group of Democratic lawmakers[166] urging the ban to be lifted, the FDA stated on June 14 that it had no plans to change the regulation and will reevaluate its policies "as new scientific information becomes available.

[192] On June 14, two dozen news agencies sent a four-page letter to Orlando's city attorney jointly demanding the release of recordings that 911 callers made on the night of the shooting.

Requests to release recordings of 911 calls, police radio transmissions, and the exchanges between law enforcement and Mateen were denied, citing disagreements over whether they fall under local or federal jurisdiction.

[211] On October 31, the City of Orlando released nearly 30 minutes of recordings of police negotiators talking with Mateen during the course of the shooting, after a judge with the Ninth Judicial Circuit Court of Florida ruled that these calls should be made public.

[224] On November 8 the City of Orlando announced its plans to purchase the Pulse nightclub later that month for $2.25 million and turn the site into a memorial for the victims and survivors of the shooting.

[62] According to Senator Ron Johnson, Mateen searched online for references to the shooting during the attack, and made posts on Facebook expressing his support for Islamic State, saying "You kill innocent women and children by doing us [sic] airstrikes.

The 2013 investigation was opened after he made comments to coworkers about being a member of Hezbollah and having family connections in al-Qaeda,[244] and that he had ties to Nidal Hasan—perpetrator of the 2009 Fort Hood shooting—and Dzhokhar and Tamerlan Tsarnaev—perpetrators of the Boston Marathon bombing.

[250] On July 26, a Senate homeland security committee chairman sent a four-page letter to the inspector general of the U.S. Department of Justice (DOJ) requesting an independent review of the FBI's 2013 and 2014 investigations.

[158][255][256] Investigators have said no evidence linking Mateen to the group has emerged, and have cautioned that the shooting may have been IS-inspired without being IS-directed,[257] as was the case in the December 2, 2015, attack in San Bernardino, California.

[275] During the trial, the prosecution revealed it withheld information during discovery that Salman's confession of helping scout potential attack locations was not true based on cell phone evidence, and that the FBI knew this even though it had been used to deny her bail.

[277][278] In July 2016, law enforcement officials reported that the FBI—after conducting "interviews and an examination of his computer and other electronic media"—had not found any evidence that Mateen targeted Pulse because the nightclub was a venue for gays or whether the attack was motivated by homophobia.

"[283] In April 2017, the Orlando Sentinel obtained a copy of a 78-page presentation given by Mina to some ten police groups located around the world, which discussed the OPD's response to the attack and what it has learned.

The presentation offered a comprehensive timeline of the attack and included diagrams and still photos from body camera footage showing officers in their initial confrontation with Mateen.

[305] Countries that released their own statements condemning the shooting include Afghanistan, Egypt, Saudi Arabia, Qatar, Iran, the United Arab Emirates, Kuwait, and Turkey.

[306] Many people on social media and elsewhere, including 2016 United States presidential election candidates, members of Congress, other political figures, foreign leaders, and various celebrities, expressed their shock at the event and extended their condolences to those affected.