Republicans briefly brought the Democrat-led impeachment investigation to a halt on Wednesday when around two dozen House members stormed into a closed-door deposition with a Defence Department official.
Democrats said the move compromised national security because some of the Republicans took electronic devices into a secure room.
The protest captured national attention, drawing the focus away from the testimony of a top US diplomat who told politicians just a day earlier that he was told President Donald Trump was withholding military aid from Ukraine unless the country’s president pledged to investigate Democrats.
The manoeuvre delayed a deposition with Laura Cooper, a senior Defence Department official who oversees Ukraine policy, until mid-afternoon.
The interview began some five hours behind schedule, after a security check by Capitol officials, and ended after roughly four hours.
As a series of diplomats have been interviewed in the impeachment probe, many Republicans have been silent on the president’s conduct. But they have been outspoken about their disdain for Democrats and the impeachment process, saying it is unfair to them, even though they have been in the room questioning witnesses and hearing the testimony.
“The members have just had it, and they want to be able to see and represent their constituents and find out what’s going on,” said Jim Jordan, the top Republican on the House Oversight and Reform panel.
That committee is one of three leading the investigation, and its members are allowed into the closed-door hearings.
Politicians described a chaotic scene.
Democrat Debbie Wasserman Schultz said she had just walked into the room when the Republicans barged past Capitol police officers and Democratic staffers. The staff member who was checking identification at the entrance was “basically overcome” by the Republicans, she said.
“Literally some of them were just screaming about the president and what we’re doing to him and that we have nothing and just all things that were supportive of the president,” Ms Wasserman Schultz said.
Later, when the deposition began, Ms Cooper answered questions in response to a subpoena, an official working on the impeachment inquiry said.
She explained the process of distributing military aid and was asked whether the appropriate steps were followed on Ukraine, according to a person familiar with the interview.
“The president’s allies in Congress are trying to make it even more difficult for these witnesses to co-operate,” said Adam Schiff, chairman of the House Intelligence Committee.
Democrats deny that Republicans are being treated unfairly, noting that they have had equal time to question witnesses and full access to the meetings.
Mr Schiff said closed-door hearings are necessary to prevent witnesses from concealing the truth and has promised to release transcripts when it will not affect the investigation.
Democrats also said the Republicans – several of whom do not sit on one of the three committees – compromised security at Wednesday’s closed-door deposition.
The interviews are being held in what is called a Sensitive Compartmented Information Facility, or SCIF, which is a secure room where members can hear classified information.
Several politicians leaving the facility said some of the Republicans took their mobile phones, even though electronics are not allowed.
All members of Congress are familiar with the protocol of the SCIF, since they are often invited to classified briefings, and there are several such rooms around the Capitol.
Several Republicans appeared to be tweeting from the secure room. Mark Walker tweeted: “UPDATE: We are in the SCIF and every GOP Member is quietly listening.”
Bennie Thompson, who chairs the House Homeland Security Committee, alleged that Republicans “intentionally brought their electronic devices” into the secure area, violating congressional rules and the oath they take to gain access to classified information.
The “unprecedented breach of security raises serious concerns” for committee chairs who maintain secure facilities in the Capitol, Mr Thompson wrote in a letter to the House sergeant at arms asking for action to be taken against members of Congress involved in the breach.
Senator Lindsey Graham criticised his Republican colleagues for the tactic, calling them “nuts” to make a “run on the SCIF”.
“That’s not the way to do it,” he said.
He later tweeted that he initially believed Republicans had taken the room by force and that it was actually a “peaceful protest”, adding that his House colleagues had “good reason to be upset”.
The Republicans who took part in the protest were unbowed.
Steve Scalise, the No 2 House Republican, said Democrats are running a “Soviet-style process” that should “not be allowed in the United States of America”.
“We’re not going to be bullied,” he said.
The stand-off came the day after William Taylor testified that he was told Mr Trump withheld military aid to Ukraine until the country’s president went public with a promise to investigate Democrats.
Mr Trump wanted to put Ukraine’s leader “in a public box”, Mr Taylor recalled.
Democrat Ted Lieu said Republicans did not want to hear from Ms Cooper because they were “freaked out” by that testimony.
“They know more facts are going to be delivered that are absolutely damning to the president of the United States,” he said.