Ron Johnson, the Republican chairman of the Senate Committee on Homeland Security, sent a letter to Facebook chief Mark Zuckerberg Wednesday asking the company to share specifics of five accounts apparently used by Mateen.

Lawmakers are trying to determine if there are ways for intelligence and law enforcement communities to monitor social media platforms like Facebook “so that we can prevent these tragedies,” Johnson told CNN on Thursday.

“This is our job, to see what has happened in the past, what can we possibly do to prevent this from occurring in the future and how can we find bipartisan solutions,” the Republican said.

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In his letter to Zuckerberg, Johnson said Mateen apparently posted sometime during the attack that he was pledging allegiance to the Islamic State group’s leader, and “America and Russia stop bombing the Islamic state.”

He also allegedly posted: “The real muslims will never accept the filthy ways of the west” and “In the next few days you will see attacks from the Islamic state in the usa.”

Mateen also allegedly searched for “Pulse Orlando” and “Shooting,” Johnson said.

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A Facebook spokeswoman confirmed the company has received the senator’s letter, which asked Facebook to provide investigators with details of Mateen’s Facebook accounts and activity.

She said Facebook had not yet responded to the request but has been working with law enforcement from the outset of the investigation.

Also Thursday, CNN reported that Mateen’s wife suspected he was going to carry out an attack that night, even though he told her he was going out to see a friend.

When the news of the shooting broke, 30-year-old Noor Mateen called him frantically, CNN said, citing unidentified sources. He didn’t pick up, but texted her about 4 am asking if she had seen the news.

She responded: “I love you,” the report said.

Authorities have refused to comment on reports that Mateen’s wife would face charges over her alleged knowledge of Mateen’s intentions to carry out an attack.