Eric Swalwell was among the last lawmakers to leave the House floor during the Capitol attack. Here's what he saw

As the angry mob of President Trump's supporters pushed and pounded on the doors of the House of Representatives Chamber, intent on stopping the certification of the election, Rep. Eric Swalwell, D-Dublin, tore off his suit coat and girded for the chambers to be invaded.

With Rep. Ruben Gallego, D-Ariz., Swalwell was one of the last members of Congress to leave the House floor, sticking around to make sure everyone was out and yelling directions to panicked people in the gallery above as sergeants at arms piled furniture against the doors.

In retrospect, he said, he wished they'd stayed — to stand up to the protesters and for democracy.

"There was a mob outside, and the chamber was about to be overrun," he said. "I understand why we had to leave, but I regret having left."

Swalwell is stunned by the seeming ease with which the angry rioters stormed into the Capitol and rampaged through its hallways after a rally near the White House where Trump made remarks that incited the crowd.

"I thought it was one of the safest places, one of the most heavily fortified places in the world," Swalwell said. "That's one of the most unsettling things about the day. It is such a sacred, symbolic and fortified space. I am still in disbelief."

California lawmakers were scattered throughout the Capitol building during the insurrection, ordered to hunker down in safe places and urged to grab gas masks and remove the lapel pins that identify them as members of Congress.

It was "a very sad day," said Rep. Mike Thompson, D-St. Helena, a veteran of the Vietnam War. It was, he added, "an embarrassing day for the United States of America."

Back in his Tri-Valley district Saturday, fresh from a jog, Swalwell said the chaotic scene in the decorous halls of the Capitol was more infuriating than frightening.

"I was angry," he said. "And still am."

Swalwell said he knew the attack on the Capitol was serious as he sat with his friend Gallego, reviewing remarks the Arizona congressman was preparing to present in the debate over his state's certification of the election. He knew from Twitter that an angry mob was trying to break into the Capitol and that things were concerning enough that Speaker Nancy Pelosi had been ushered out of the room.

Then Swalwell got a text from Gallego's wife asking him not to leave without her husband.

An order to don gas masks stored under their seats came quickly. Swalwell said he pulled out his mask and looked at it, confused.

"I couldn't tell it from a newspaper," he said.

For Gallego, a Marine Corps veteran, it was second nature. He helped Swalwell, then realized others could use help, too. He started barking out instructions, advising people not to breathe too quickly or too deeply. When they were directed to leave, Swalwell found Gallego hanging back, standing on a chair and yelling directions to people in the gallery. Swalwell helped Gallego after realizing what he was doing.

"I thought I'd have to fight my way out," Gallego told the Washington Post.

After seeing Gallego and others take charge, Swalwell said, he has a new respect for military veterans in Congress.

"They bring a lot of experience and insight into Congress," he said, "but in a situation like that, they brought a lot of help to their colleagues."

Swalwell and Gallego were escorted off the floor, with just the sergeants at arms remaining to hold back the mob.

"Move, move, move," their escorts shouted as they headed along an evacuation route, Swalwell recounted. "You could heard the yelling, the breaking of glass, the gunshot" that killed rioter Ashli Babbitt, an Air Force veteran and Trump supporter from San Diego, he said. Swalwell said he did not see the shooting.

For five hours, the House members and some staff and journalists remained hunkered in a safe room that some feared would be discovered by the invaders, Swalwell said. Getting updates from their phones, they heard that there were buses outside, possibly to evacuate the lawmakers.

"We feared that we might have to leave the area, which I did not want to do," he said. "The people I was talking to did not want to leave. We thought it was important that we did not look like we got run out."

They stayed, reconvened after the Capitol was cleared of rioters and completed the certification of the election. The streets were empty and quiet as Swalwell drove himself home at about 4 a.m., he said.

"It was an unceremonious ending to a sad day in our country's history ... one that can never happen again," he said.

With threats of another attack on the Capitol on Jan. 17 and fears of Inauguration Day disturbances on Jan. 20, Swalwell said it's critical to ensure that President-elect Joe Biden is sworn in without more disruption.

"The most important thing we can do is show the nation and the world that we can deliver a peaceful transition of power, that we can be sure the public can bear witness to in a safe way and that we can't be intimidated," he said.

Swalwell considers Trump's impeachment necessary.

"He's a danger to our life and to our ideals," he said. "He's going be gone in 250 hours, but as we've seen, in minutes, he can incite an attack on the Capitol."

San Francisco Chronicle staff writer Tal Kopan contributed to this report.