The FBI fired agent Peter Strzok on Friday over anti-Trump text messages he exchanged with former agency lawyer Lisa Page during the 2016 presidential campaign, Strzok's lawyer, Aitan Goelman, confirmed Monday.

Strzok, who led the FBI's investigation into Russian meddling in the election, was ordered dismissed by FBI Deputy Director David Bowdich, Goelman told CNBC.

Bowdich's decision overruled a previous FBI finding that Strzok should face a demotion and 60-day suspension.

"This decision should be deeply troubling to all Americans," Goelman said in a statement Monday.

The lawyer accused Bowdich of bowing to political pressure and said the firing was not based "on a fair and independent examination of the facts."

President Donald Trump has repeatedly cited the texts between Page and Strzok, who were dating during the 2016 campaign, as proof that the FBI's investigation was tainted from the start.

The texts were cited in a 500-page report released in June by the Justice Department's inspector general.

Inspector General Michael Horowitz found that FBI Director James Comey was "insubordinate" in handling the probe into Hillary Clinton's private email use, damaging the agency and its image of impartiality — though the investigation was not motivated by politics.

In one instance of bias, Horowitz cited this text exchange between Strzok and Page on Aug. 8, 2016.

Page questioned whether Trump would become president.

Strzok replied: "No. No he's not. We'll stop it."

Page, who served as an FBI lawyer and close adviser to former FBI Deputy Director Andrew McCabe, resigned from the bureau in May.

Mueller had removed Strzok from his team after the anti-Trump texts were released.

In heated testimony on Capitol Hill last month, Strzok vehemently denied any bias in the Russia probe, telling members of the House Oversight and Judiciary committees in a joint session: "Like many people, I had and expressed personal political opinions during an extraordinary presidential election.

"My opinions were expressed out of deep patriotism," he said.