Republican presidential candidate Sen. Rand Paul (R-KY) speaks during the CNN republican presidential debate at The Venetian Las Vegas on Dec. 15, 2015 in Las Vegas, Justin Sullivan/Getty Images

During Tuesday night’s Republican presidential debate, the candidates argued over how the United States should be protecting itself from terrorists, but not everyone on stage had a firm grip on the facts. While criticizing Florida Sen. Marco Rubio’s stance on immigration, Kentucky Sen. Rand Paul blamed lax immigration policies for all the terrorism the U.S. has experienced in recent years.

“Every terrorist attack we've had since 9/11 has been legal immigration,” Paul said. “Marco wants to expand that. I want more rules, more scrutiny; and to defend the country, you have to defend the border.”

But, as you might be able to guess, Paul’s claim that every terrorist attack over the past 15 years has been carried out by someone who legally immigrated to the U.S. is not true. The most obvious example should have been familiar to Paul, as Republicans frequently referred to the recent shootings in San Bernardino, California, throughout the debate.

While Tashfeen Malik, the woman involved in the shooting, did come to the U.S. from Saudi Arabia on a fiancée visa, the man she was coming to meet, Syed Farook — the other shooter — was born in Illinois. Farook was a Muslim, but that did not make him any less an American citizen.

Terrorist Attacks and Threats in United States | FindTheData

San Bernardino is not the only example of a terrorist attack carried out by someone born in the U.S. Another notable incident is the shooting that took place in 2009 at Fort Hood in Texas. Nidal Hasan, an army major born in Virginia, killed 13 people after becoming radicalized during his time in the military.

A third example could be the shooting in Charleston, South Carolina, this summer in which Dylann Storm Roof, a white 21-year-old, killed nine black people at a church. While the FBI was hesitant to label the incident as terrorism, many others — including former Attorney General Eric Holder — did so.

Furthermore, there have been studies that show most terrorists are U.S.-born citizens. Data from the New America Foundation show 80 percent of terrorists attacks since 9/11 have been committed by U.S. citizens, and 64 percent were born in the U.S.

Despite this evidence, Paul during the debate touted an amendment he introduced last week that would require the U.S. to stop admitting immigrants from the Middle East or “countries with a high risk of terrorism.”

“We have to have a pause on immigration from the Middle East till [sic] we can get a handle on 'are we admitting people who want to attack and kill us?'” Paul said on CNN last week.

Paul is far from the only Republican presidential candidate to hold these kinds of views. Donald Trump has come under intense criticism for proposing the U.S. ban all Muslims from entering the country, and other candidates have proposed religious tests that would allow only Christian refugees from countries like Syria or Iraq.