Sen. Lindsey Graham (R-SC) told Fox News that the Orlando terrorist may have been stopped if the FBI had kept an eye on him.
Graham said that under the policies of the Obama administration, cases like Omar Mateen's are investigated in the same way as other crimes.
The FBI investigated Mateen in 2013 and again in 2014, but eventually the file was closed.
Graham said the case was closed because the Obama administration "treats radical Islamic threats as common crimes."
"I'm not trying to solve a crime, I'm trying to prevent an attack. And if we had kept the file open and we saw what he was up to, I think we could have stopped it," said Graham, noting that Mateen should have been monitored because of what he said and did previously, not because he was a Muslim.
The FBI investigated Mateen for 10 months, but did not find evidence that he had committed a crime or directly supported terrorism.
Meantime, Fox News chief intelligence correspondent Catherine Herridge reported on Outnumbered that the connection between Mateen and an American suicide bomber in Syria was much "deeper" than previously understood by federal investigators.
Watch her report above and read more at FoxNews.com.