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Hillary Clinton on Monday said the “mind numbingly familiar” attack at an Orlando nightclub makes clear the U.S. “must defeat” ISIS and proposed beefing up intelligence gathering tools to help better identify lone wolf attackers.

“The Orlando terrorist may be dead. But the virus that poisoned his mind is very much alive,” Clinton said at an event in Cleveland.

A gunman killed 49 people at a gay club in Orlando early Sunday before being killed in a shootout with police. The attacker, 29-year-old Omar Mateen, had sworn allegiance to ISIS in a 911 call shortly before the attack, according to law enforcement.

Mateen had been on the FBI’s radar since 2013, but he was not under surveillance when he carried out the deadliest mass shooting in U.S. history.

“The attack in Orlando makes it all the more clear, we cannot contain this threat, we must defeat it,” Clinton said.

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The former secretary of state said identifying lone wolf shooters like Mateen and the couple that carried out last year’s shooting in San Bernardino, California, would be a “top priority.” Clinton advocated for beefing up intelligence gathering tools for law enforcement and working with local leaders to identify signs of radicalization.

Clinton also pledged to continue to advocate for gun reform, calling for a ban on the type of assault rifle used by Mateen and saying someone under FBI suspicion should not be allowed to purchase firearms.

“If the FBI is watching you for suspected terrorist links, you shouldn’t be able to go buy a gun, no questions asked,” Clinton said.

Though she declared it was “not a day for politics,” Clinton took a clear shot at GOP rival Donald Trump’s proposal to ban Muslims from entering the U.S., saying the community is best prepared to identify the warning signs of radicalization.

“Inflammatory, anti-Muslim rhetoric and threatening to ban the families and friends of Muslim-Americans, as well as millions of Muslim business people and tourists from entering our country, hurts the vast majority of Muslims who love freedom and hate terror,” Clinton said.

And in speaking to LGBT Americans, who have been reeling since the attack on a popular gay club, Clinton reiterated her pledge to stand up for gay rights.

“We’ve seen too many examples of how the struggle to live freely, openly and without fear has been met by violence,” Clinton said. “We have to stand together, be proud together.”