"Do something. You can."

That was Cleopatra Cowley-Pendleton's plea to Congress this afternoon, hours before she was to appear in the guest box of first lady Michelle Obama during the State of the Union address. The Pendletons lost their daughter Hadiya in January. She was shot, police believe, by Chicago gang members. The 15-year-old drum majorette had returned from Washington just days earlier; she had participated in the president's second inaugural festivities.

"No one should feel the way we do and I'm appealing to Congress to be smarter than me. You guys signed up for the job," the mother said.

The Pendletons are among at least 42 victims of gun violence who were invited to President Obama's address tonight, including family members of victims of the Dec. 14 elementary school shooting in Newtown, Conn., where 20 first graders and six adults were killed. The guests were invited by the White House and dozens of lawmakers.

Check Out More ABC Coverage of the 2013 State of the Union Here

Today Cowley-Pendleton and other guests spoke in the Capitol about what they want from Congress and the Oval Office. The guests formed in the Gabe Zimmerman Meeting Room, named for the congressional aide who was fatally shot in 2011 when a gunman opened fire on then-Rep. Gabrielle Giffords and the crowd around her at an event in Tucson, Arizona. Zimmerman's mother and fiancee were among the participants in the photo opportunity today.

Emily Nottingham said her son kept pictures of the Lincoln Memorial on his personal computer.

"What Gabe liked and loved - Washington, D.C. buildings and memorials and museums - was because of what they stood for," she said. "The best of government. The best of our government's ideals. He believed, and he was not naive, he knew that government processes are long, politics are messy, and he believed anyway that eventually our legislators stand up and do the right thing for Americans."

Also in attendance was Elvin Daniel of McHenry, Illinois. Daniel, a hunter and long-standing member of the National Rifle Association, lost his sister, Zina Haughton, when she was killed by her husband in a shooting rampage. Local media reported that days earlier she had obtained a restraining order against her husband that would have barred his ownership of a firearm.

Choking back tears today, Daniel urged government to approve universal background checks for all gun purchases.

"We do need to do background checks on people. The president is definitely on the right track," he said, adding that his sister "was full of goodness, and some goodness will come out of her death. This is the time and place."

INFOGRAPHIC: Guns in America: By The Numbers

Many members of Congress who had invited the guests were present for the remarks, wearing green and white ribbons in memory of the victims. The lawmakers had themselves been personally affected by gun violence in the past. They were led by Rep. Jim Langevin, D-R.I., who as a 16-year-old was critically injured in an accident while working with the Warwick Police Department in the Boy Scout Explorer program. An officer handling a pistol, not realizing there was a round in the chamber, pulled the trigger. The bullet bounced off a locker and struck Langevin in the neck, severing his spinal cord and paralyzing him.

Representatives of the Brady Campaign Against Gun Violence, the Million Mom March, and Mayors Against Illegal Guns were also present for the event.

Not all victims of gun violence present on Capitol Hill today had come to petition for strengthened gun control measures. Testifying before the Senate Judiciary Committee this morning, one victim, Suzanna Hupp, told lawmakers that had she not complied with state gun laws and left her firearm in her car, she might have helped stop the gunman in a 1991 massacre in Killeen, Texas that left 23 dead and scores more wounded.