ORLANDO, Fla. (AP) -- While his victims texted heartbreaking last words to loved ones from the blood-drenched floors of packed bathrooms, Omar Mateen apparently turned to social media to measure the viral shockwaves his attack on a gay nightclub had generated.
As this grief-stricken city prepares to bury the first of the 49 who perished at the Pulse dance club, a Senate Committee has asked Facebook CEO Mark Zuckerburg for help uncovering the trail of hate Mateen left behind in cyberspace.
"The real muslims will never accept the filthy ways of the west," the 29-year-old American-born Muslim wrote on one of at least five Facebook accounts believed to be associated with him, according to the letter from Sen. Ron Johnson, chairman of the Senate Homeland Security Committee.
The call comes as President Barack Obama prepares to visit Orlando on Thursday. On Wednesday, drag queens and motorcyclists paid their respects at a visitation for Javier Jorge-Reyes, beginning the long procession of rainbow-hued sendoffs for Mateen's victims.
In the letter released Wednesday, Johnson, a Wisconsin Republican, said the security guard and wannabe police officer took time Sunday to search on Facebook for "Pulse Orlando" and "Shooting." The attack took place early that morning.
The letter also said Mateen made a series of Facebook posts in addition to performing the searches, and that the activity online took place before and during his attack. It does not specify what took place when.
A person familiar with the situation who is not authorized to speak publicly said the Facebook posts came moments before the attack began.
"America and Russia stop bombing the Islamic state," he wrote that morning, according to the letter. As he did in his call to a 911 operator during the massacre, Mateen pledged his allegiance on Facebook to the leader of the Islamic State and, in his final post, warned: "in the next few days you will see attacks from the Islamic state in the usa."
The committee asked Facebook to produce information on Mateen's online activity and to provide a briefing to the panel. A spokesman for the FBI did not immediately return a call for comment, and Facebook had no immediate comment.
The three-hour rampage began at 2 a.m. Sunday and ended with Mateen being killed by a police SWAT team. The FBI said it is still gathering evidence at Pulse and analyzing cellphone location data to piece together Mateen's activities leading up to the massacre.
On Saturday night, hours before the rampage, Mateen visited Disney Springs, an outdoor restaurant, retail and entertainment complex at Walt Disney World, an official who was briefed on the case but insisted on anonymity to discuss the continuing investigation told The Associated Press.
The official said it is not clear what Mateen was up to.
A key topic for investigators is how much Mateen's Palestinian-American wife may have known about the plot. An official who was briefed on the case but insisted on anonymity to discuss a continuing investigation said authorities believe 30-year-old U.S.-born Noor Salman knew ahead of time about the attack.
Investigators have spoken extensively with her and are working to establish whether she recently accompanied Mateen to the club, said a second official who was not authorized to discuss the case publicly.
U.S. Attorney Lee Bentley repeatedly refused to say whether charges might be brought against the wife or anyone else.