House Speaker Mike Johnson, R-La., joins 'The Sunday Briefing' to discuss the arrest of an alleged pro-Hamas attacker in Louisiana, the state of the ceasefire between Israel and Hamas and George Santos' release from prison.

A suspected terrorist allegedly linked to the Oct. 7, 2023, Hamas attack on Israel has been arrested in Louisiana. House Speaker Mike Johnson called the revelation "alarming," blaming the former Biden administration's border policies for allowing the suspect into the country.

"I had no idea. It's alarming to all of us, but I'm certainly glad that we have an administration who is prioritizing rounding up these dangerous people. It's a great relief to a lot of folks down there," Johnson said on "The Sunday Briefing."

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Mahmoud Amin Ya'qub Al-Muhtadi, a Gazan native living in Louisiana, was arrested by the FBI in early October. The Justice Department said Al-Muhtadi was an operative of a paramilitary group that participated in Hamas' 2023 attack on Israel.

The Oct. 7, 2023, Hamas assault on Israel killed roughly 1,200 people, according to Israeli officials, and sparked the ongoing war in the Middle East that has killed tens of thousands in Gaza.

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U.S. Customs and Border Protection (CBP) said records show the suspect entered the United States in September 2024, nearly a year after the attack, using a fraudulently obtained visa.

"After hiding out in the United States, this monster has been found and charged with participating in the atrocities of October 7 -- the single deadliest day for Jewish people since the Holocaust," Attorney General Pamela Bondi said in a press release.

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Johnson and other Republicans have been frequent critics of the former Biden administration's border and immigration policies. A study from the Pew Research Center found that the "unauthorized immigrant population" rose to a record 14 million in 2023.

"They had a wide-open border," Johnson said, warning that the impacts could last for decades to come.

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"We know that terrorists got across the border, and I don't think anybody on planet Earth can discern exactly how many. We'll be living with the threat and the ramifications of that open border, probably for the rest of our lives," he said.

Johnson calls FBI's 'alarming' arrest of alleged Hamas terrorist proof of Biden immigration failures