Omar Mateen reportedly checked Facebook to see if the Orlando mass shooting was trending before he was killed by police on Sunday.
According to a letter from Sen. Ron Johnson, chairman of the Senate Homeland Security Committee, Mateen searched for the terms “Pulse Orlando” and “Shooting” while the attack was still going on.
In addition, he reportedly posted messages on his Facebook page while he was carrying out the deadliest mass shooting in American history.
“The real muslims will never accept the filthy ways of the west,” Mateen wrote on one of at least five Facebook accounts believed to be associated with him, according to the letter.
Mateen made several additional Facebook posts both before and during his attack. The final post allegedly read, “”In the next few days you will see attacks from the Islamic state in the usa.”
The Senate committee has asked Facebook CEO Mark Zuckerberg for help uncovering the messages and clues that Mateen left behind in cyberspace.
A person familiar with the situation who is not authorized to speak publicly told the AP that the Facebook posts came moments before the attack began. Mateen went on to kill 49 people and injure another 53 people.
“America and Russia stop bombing the Islamic state,” Mateen reportedly wrote. “In the next few days you will see attacks from the Islamic state in the USA.”
Mateen was killed by police during a shootout after a lengthy standoff with police.
Joe Otterson contributed to this report