"We can't allow him to remain in office, it's a matter of preserving our Republic and we need to fulfil our oath," Ms Omar wrote.
Congresswoman Ilhan Omar is drawing up articles of impeachment against Donald Trump as she and at least six other House Democrats have called on the President to be removed from office.
Mr Trump, who has just 14 days left in office, has been accused of inciting the riotous mob that stormed the US Capitol on Wednesday pushing past police officers and ramming their way into the Senate and House chambers.
The chaos interrupted a joint session of Congress where lawmakers and Vice President Mike Pence were slated to certify Joe Biden's victory after hearing Republican challenges to the 2020 presidential election results.
"I am drawing up Articles of Impeachment. Donald J. Trump should be impeached by the House of Representatives and removed from office by the United States Senate," Ms Omar, a second-term Minnesota Democrat, tweeted on Wednesday.
"We can't allow him to remain in office, it's a matter of preserving our Republic and we need to fulfil our oath," Ms Omar wrote.
Ms Omar was joined by a growing chorus of voices in the House Democratic caucus calling for the President's immediate removal as law enforcement continued clearing and securing the Capitol grounds on Wednesday.
"This is on Donald Trump, period. He called folks to D.C. and gave them marching orders. He needs to be impeached and removed immediately," tweeted Michigan Congresswoman Rashida Tlaib.
But it wasn't just the "Squad" of progressives urging their colleagues to constitutionally purge Mr Trump from office in the final days of his presidency.
Congressman Seth Moulton, a moderate Democrat from Massachusetts, was one of the handfuls of lawmakers issuing such calls on Wednesday.
"Trump is directly responsible for this insurrection and violence. He needs to be removed from office immediately. It is the constitutional responsibility of Vice President Pence and the cabinet to exercise power granted them by the 25th amendment," Mr Moulton tweeted.
He added: "Or Congress must immediately impeach and remove the President for the safety of our nation."
By 5 pm Wednesday, no Republicans had mentioned anything about removing Mr Trump from office as law enforcement appeared to be getting a better handle on the Capitol's insurrection on Wednesday.
But several of them placed blame for the chaos in Washington squarely on the outgoing President's shoulders.
"This is what the president has caused today, this insurrection," Utah Senator Mitt Romney told the New York Times' Jonathan Martin on Wednesday as throngs of pro-Trump rioters were storming the Capitol.
Mr Romney was the only Republican senator to vote to convict Mr Trump at his impeachment trial last year.
The President was impeached in the House for withholding military aid to Ukraine in 2019 unless the Eastern European country's new President announced a bogus anti-corruption investigation into Mr Biden. The latter at the time was a candidate for the 2020 Democratic presidential nomination.
In February 2020, the Senate voted to acquit Mr Trump on a mostly party-line basis, with Mr Romney the only senator from either side crossing the aisle.
By mid-afternoon on Wednesday, lawmakers and staff had been evacuated from the building after initially being told to "hide or seek cover" and "remain quiet".
Several national reporters inside the Capitol on Wednesday reported overhearing US Capitol Police saying "shots fired" over the radio.
At least one woman was reportedly shot outside the House chamber, according to reports. She was carried out of the building on a stretcher in critical condition.
Some rioters even made it inside the Senate chamber, with one man taking the dais and declaring, "Trump won that election."
At least one rioter made his way into Speaker Nancy Pelosi's office, taking pictures and issuing an apparent threat about the election results.
"We will not back down," the rioter wrote in red Sharpie in all capital letters on a manilla folder.
Scores of other Republican lawmakers have denounced the pro-Trump rioters storming the Capitol, with at least one military veteran in Congress comparing the scene in Washington on Wednesday to his time in the Middle East in the 2000s.
"I haven't seen anything like this since I deployed to Iraq in 2007," said GOP Congressman Mike Gallagher of Wisconsin.