Kelly O'Brien, fiance of Congressional staffer Gabe Zimmerman, who was killed in the shooting rampage in Tucson, Ariz., accompanied by Sen. Frank Lautenberg (D-N.J.), right, speaks during a news conference on Capitol Hill in Washington, Tuesday, April 12 (J. Scott Applewhite/AP)

O’Brien, a soft-spoken nurse, was in Washington Tuesday morning to speak out publicly against high-capacity magazines like the one used in January’s shooting spree in Tucson that wounded 13 and killed six, including O’Brien’s fiancee, Gabe Zimmerman. Zimmerman was the community outreach director for Rep. Gabrielle Giffords (D-Ariz.), who was the target of the Tucson attack. Jared Lee Loughner is accused of being the gunman.

At an emotional news conference in a small basement meeting room of the Capitol, O’Brien endorsed legislation sponsored by longtime gun-control advocates Rep. Carolyn McCarthy (D-N.Y.) and Sen. Frank Lautenberg (D-N.J.) that would ban high-capacity magazines.

“The man who killed Gabe and five others shot 31 bullets in 15 seconds, roughly two shots every second,” O’Brien said. “He stopped only when his high-capacity magazine was empty.”

O’Brien said that while she did not personally own a gun, she respected others’ Constitutional right to possess one.

“However, every Constitutional right comes with responsibility,” she continued. “It is entirely reasonable to limit gun magazines to ten bullets, as Representative McCarthy and Senator Lautenberg are proposing. Ten bullets are more than enough for self-defense, which is why many people own a handgun. ... This type of tragedy cannot be allowed to happen again.”

McCarthy, standing alongside O’Brien, put her arm around O’Brien after she finished speaking.

Also speaking at the news conference, which was organized by the Brady Campaign to Prevent Gun Violence, were Ross Zimmerman, Gabe Zimmerman’s father; and Paul Helmke, president of the Brady Campaign.

McCarthy, whose husband was killed in the 1993 Long Island Rail Road shooting, spoke out forcefully in support of O’Brien’s decision to publicly back the gun legislation in the wake of her personal tragedy.

“When we go through seeing a shooting as we saw in Arizona, for the victims, it brings us back to that moment, which is extremely painful,” McCarthy said.

“So everything that Kelly is going through right now, I have lived over and over and over again. I know how difficult it is for someone coming from outside ‘this world’ to come and speak. And I remember that there’ll be others that will say, ‘Oh, you’re going on the emotional feelings.’ You’re damn right we are. We are because the pain doesn’t go away.”

Like O’Brien, McCarthy is a nurse by training. The New York Democrat worked for more than 30 years as a licensed practical nurse before being elected to Congress in 1996, a point she mentioned in her remarks on Tuesday.

“I will say that nurses are tough,” McCarthy said. “And we can do a lot. And we can smile when we have to smile and we’ll cry when we have to cry. And I know that Kelly is taking this first step to being an activist, and that is a very, very hard step, because she’s walking into a world that people will question, why is she doing this? And people will say, would you have gotten involved in something if her fiancee, Gabe, hadn’t been murdered?”

“I can’t speak for her,” McCarthy continued. “I can say I’ve answered that question a hundred times. No, I probably wouldn’t have gotten involved. I had a good life. I had a loving family. I had plans for the future. This is what all victims go through.”

McCarthy and Lautenberg have introduced legislation that would ban the high-capacity magazines. Congress passed a decade-long on the high-capacity magazines in 1994, but the law expired in 2004.

Several lawmakers have made renewed efforts to reinstate the ban in the aftermath of the Tucson shooting, but so far the legislation has not progressed in either chamber.

McCarthy said Tuesday that she has been working deliberately, meeting with lawmakers one-on-one during the time that lawmakers gather for floor votes so that she can make her case on a personal level.

Toward the end of the news conference, O’Brien was asked what she thought Zimmerman would think of her entering the political fray over gun control legislation.

“I actually knew nothing about politics before I met Gabe, so he taught me a lot,” O’Brien said. “And he loved America and how it worked, and it made him so happy just to be a part of that.”

She paused for a moment.

“I think he would be proud.”