ORLANDO, Fla. — 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.