Mother of fallen Capitol Police officer lobbies GOP senators on Jan. 6 commission

The mother of fallen Capitol Police Officer Brian Sicknick returned to the site of the Jan. 6 attack on Thursday to lobby Senate Republicans to vote to establish a bipartisan, independent commission to investigate the assault she argues caused her son's death.

"This is why I'm here today, and I'm usually I'm staying in background, and I just couldn't -- couldn't stay quiet," she told reporters as the Senate was poised to vote on starting debate on the commission proposal -- a move Republicans have threatened to filibuster.

Sicknick was brutally attacked by rioters, video shows, and died a day later after suffering two strokes.

The Washington, D.C., medical examiner determined last month a stroke is specifically what caused Sicknick's "natural" death.

Gladys Sicknick was joined by Sicknick’s longtime partner, Sandra Garza, and former Republican Rep. Barbara Comstock, an ABC News contributor, along with U.S. Capitol Police Officer Harry Dunn and Metropolitan Police Officer Mike Fanone.

"If January 6th didn’t happen, Brian would still be here," Dunn said at an emotional news conference outside Republican Sen. Mitt Romney's office, the first Senate Republican to say he'd support the commission.

Sicknick's mother made clear she came with the goal to persuade lawmakers on the fence to vote for the commission. She was scheduled to also sit down with Sen. Susan Collins of Maine -- who supports a commission with an amendment -- as well as dozen others including Sens. Ron Johnson of Wisconsin, Bill Cassidy of Louisiana and Lindsey Graham of South Carolina, who are poised to vote no.

But leaving Johnson's office, Comstock, speaking for the group, said the senator "made clear that he does disagree with the commission."

In a written statement released after the meeting, Johnson said he "respectfully disagreed on the added value of the proposed commission" and remains opposed, adding "I did commit to doing everything I could to ensure all their questions will be answered."

Collins said she feels "strongly" about the need for a commission, telling reporters that lawmakers "owe it to the brave men and women who defended our lives that day and in some cases, did so at the cost of their lives."

Sen. Joe Manchin, D-W.Va., who has joined Republicans on other issues including his opposition to ending the filibuster, told ABC News Congressional Correspondent Rachel Scott, "There’s no excuse for a Republican not to vote for this unless they don’t want the truth."

Garza, Sicknick's girlfriend, said earlier outside Romney's office that members who are considering voting against the legislation should "look at the footage of what happened."

"It’s very obvious it wasn’t a peaceful day," she said, an apparent jab at Republican Rep. Andrew Clyde of Georgia who said earlier this month, "If you didn't know the TV footage was a video from January the 6th, you would actually think it was a normal tourist visit."

Garza told Scott in an emotional moment that she simply can’t understand why Republicans won’t back a commission.

"It’s very disturbing that anyone would not want to support this," she said. "Why would they not want to get to the bottom of such horrific violence? They are here today, and with their families and comfortable because of the actions of law enforcement that day so I don’t understand why they would resist getting to the bottom of what happened that day — fully understanding how to prevent it. It just boggles my mind."

Fanone, joining the group, has been vocal about the "combat" he was forced to engage in on Jan. 6. He was beaten with a flag pole, concussed and suffered a heart attack defending lawmakers during the riot -- and said Thursday he's exhausted having to relive the day.

According to accounts from Rep. Eric Swalwell, D-Calif., Fanone called House Minority Leader McCarthy to discuss what happened to him on Jan. 6 and McCarthy refused to speak with Fanone. Fanone says he has called multiple times and at one point was hung up on.

Dunn told ABC News in an exclusive interview in February he was "called a [N-word] a couple dozen times today protecting this building" and recalled telling his colleague. "Is this America? They beat police officers with Blue Lives Matter flags. They fought us, they had Confederate flags in the U.S. Capitol."

McCarthy and Senate Minority Leader Mitch McConnell announced their opposition to the commission last week -- ahead of the House vote approving the measure with 35 Republicans joining Democrats. McConnell's high-profile opposition has provided political cover for most Republicans in both chambers to reject the legislation.

Gladys Sicknick, in a letter to GOP senators requesting the meetings Wednesday night, said that her son and his fellow police officers "fought for hours and hours against those animals who were trying to take over the Capitol Building and our Democracy, as we know it."

"Not having a January 6 Commission to look into exactly what occurred is a slap in the faces of all the officers who did their jobs that day," she said in the statement.

"Because of what they did, the people in the building were able to go home that evening and be with their families," she continued. "I suggest that all Congressmen and Senators who are against this Bill visit my son’s grave in Arlington National Cemetery and, while there, think about what their hurtful decisions will do to those officers who will be there for them going forward."

ABC News' Congressional Correspondent Rachel Scott and Trish Turner contributed to this report.