"Hands off our guns, Beto," Jennifer Harrison said at The Churchill open-air food court. "You're not getting our guns. The AR-15 is no more deadly than my Ruger .45."
Harrison referred to a statement O'Rourke made during the Democrats' third primary debate on Sept. 12 when asked if he would support a mandatory buyback of assault-style weapons.
"Hell, yes, we're going to take your AR-15, your AK-47. We're not going to allow it to be used against our fellow Americans anymore," the former congressman from El Paso, Texas, said.
His viral "hell yes' statement prompted one woman to speak up at a Colorado campaign event later.
"Hell, no, you’re not," Lauren Boebert told O'Rourke.
"Shame on him for coming to Colorado to expound upon our tragedies," Boebert said at the time, reportedly referring to a 2012 shooting that killed 12 people and injured more than 50. "Those are our victims, and he came here to paint a picture for his own campaign trail and really, shame on you, sir, for doing that."
On Sunday, Harrison, from the group AZ Patriots, also took aim at O'Rourke's stance on illegal immigration. AZ Patriots says they're a group of "citizen journalists and Arizona activists." The organization posted a video of Harrison at the event to its Facebook page.
"I notice that you pander a lot to the illegal aliens and encouraging illegal immigration," she said. The crowd started to boo, and O'Rourke told them to "let her speak."
"We are a nation of laws, and I just think it's a slap in the face to every legal immigrant who has waited and paid and played by the rules to immigrate to this country, and who have respected our country, our land, our citizens, our laws," Harrison continued, "and who have gone through the process."
She added, "To just say 'everybody is welcome here, you all get free stuff and just come on over the border' is, again, a slap in the face to every legal immigrant like my mother who has come here legally."
The crowd started shouting at Harrison before O'Rouke responded, taking the opportunity to address immigration rather than gun confiscation.
"Listen, on this much we can agree: There should be a safe, legal, orderly, quick path to come here to join family, to work a job, to be able to go to school, to flee persecution or, in some countries, death," he said. "I want to work with you to make sure our immigration and asylum laws achieve that purpose."
"But, what is a slap in the face to my conscience and the best traditions of this country is taking kids from their parents and putting them in cages," O'Rourke continued.
"We in this country have lost the lives of seven children in our custody and in our care. There are tens of thousands waiting on the other side of the border in an Orwellian-named migrant protection protocol [...] -- vulnerable, penniless, frightened," he said. "They're being preyed upon [by] those who exploit [people] who have no defense left."
O'Rourke added, "If immigration is a problem, it is the best possible problem this country could have. I want those asylum seekers here in this country. I want us to live according to our conscience, to our laws, to our commitments and to the best, boldest, brightest future we could possibly have."
He concluded, "Those immigrants pose no threat to you or me. Stop trafficking in these lies."
Fox News' Madeleine Rivera in Phoenix and Sam Dorman contributed to this report.