The Republican mayor of El Paso, Texas, said that President Donald Trump mocked him as a fake Republican last week during his visit to the border city following a deadly mass shooting there.

Dee Margo told PBS' "Frontline" in an interview - excerpts of which were published Wednesday - that Trump called him a RINO, a derisive moniker meaning "Republican in Name Only," when the two met after the president visited hospital staff and shooting survivors. The shooting, which targeted Latino immigrants, left 22 people dead and dozens injured earlier this month.

According to Margo, Trump was still steaming over a back-and-forth they had in February over his long-promised wall on the U.S.-Mexico border.

“He said, ‘You’re a RINO,’ and I said, ‘No sir, I’m not a RINO, I simply corrected the misinformation you were given by our attorney general, and that’s all I did’,” Margo told "Frontline," adding that the president grinned when the mayor pushed back against the nickname.

RINO is often used by Republicans to disparage others within the party who are not sufficiently conservative.

Trump sharply criticized the mayor in February during an El Paso campaign rally, saying Margo and others were "full of crap" for saying portions of the wall built nearby did not reduce crime in the city.

"And I don’t care if a mayor is a Republican or a Democrat, they’re full of crap when they say it hasn’t made a big difference," Trump said at the time. Margo excoriated Trump when he made similar comments during his State of the Union address earlier this year.

"El Paso was NEVER one of the MOST dangerous cities in the US. We‘ve had a fence for 10 years and it has impacted illegal immigration and curbed criminal activity. It is NOT the sole deterrent. Law enforcement in our community continues to keep us safe," Margo tweeted in February.

El Paso was NEVER one of the MOST dangerous cities in the US. We‘ve had a fence for 10 years and it has impacted illegal immigration and curbed criminal activity. It is NOT the sole deterrent. Law enforcement in our community continues to keep us safe #SOTU — Mayor Dee Margo (@mayor_margo) February 6, 2019

Margo quipped at the "full of crap" remark, telling "Frontline" that "I've been to a proctologist and I'm doing much better." He added that he hoped after their conversation that Trump “wouldn’t say that now."

A physical barrier would not have prevented the Aug. 3 attack in an El Paso Walmart, which authorities said was carried out by a 21-year-old American man who wanted to target people of Mexican descent. Trump, who has called immigrants rapists, criminals and an infestation, rejected that his rhetoric contributed to the violence, calling his critics "political people."

Margo told Frontline that as the two discussed immigration and border security, he told Trump that a border wall is not a “panacea.”

“I said, ‘If you want to deal with immigration, the first thing you do is you have Homeland Security define what is a secure border and what they need in the way of resources to handle that,’” Margo told the network. He added that his comments refuting misinformation about crime in El Paso seemed to “resonate” with Trump.

The White House did not respond to a request for comment.