A READER contacted us last week after we published a list of some of the lives that have been lost in mass shootings in the United States. "I in no way mean to nitpick, however, you've regrettably not included the mass shooting that took place on Feb. 14, 2008, at Northern Illinois University in DeKalb, Ill.," wrote Joe Palmer. He then listed the names of those killed: Gayle Dubowski, 20; Catalina Garcia, 20; Julianna Gehant, 32, Ryanne Mace, 19; Daniel Parmenter, 20.

Mr. Palmer was right. The DeKalb shooting was not listed. Nor was the March 12, 2005, shooting at the Living Church of God in Brookfield, Wis., that killed seven people. Or the Oct. 12, 2011, shooting at a beauty salon in Seal Beach, Calif., that killed eight people. Or the Sept. 27, 2012, shooting at the Accent Signage Systems in Minneapolis that killed six people. Sadly, we could go on — and that in itself is stark commentary about the epidemic of gun violence in this country.

"How can this be happening again? Why is no one doing anything?" Those are the questions that Mary Kay Mace told us she asks herself every time she hears of a mass shooting. Ms. Mace lost her only child, Ryanne, nearly 10 years ago when a gunman stormed into a Cole Hall lecture room at Northern Illinois University, west of Chicago. Ryanne, pronounced "Ryan," was an honors student who wanted to be a psychologist. On the day she died, she updated her MySpace.com page to read, "Happy Valentine's Day Everybody!" and underneath: "Saying you love someone is not enough, it's how you treat them that shows your true feelings."

Daniel Parmenter, also killed that day, had just called his mother to wish her a happy Valentine's Day. Catalina Garcia loved working with children and wanted to be a teacher. Julianna Gehant was also studying to be a teacher after 12 years of military service. And Gayle Dubowski was an anthropology major with a reputation for asking good questions.

"These lives lost are real people, with real hopes and real families," wrote Mr. Palmer, who attended and graduated from NIU on a scholarship created in memory of the slain students, and "it is real easy to feel like the people you miss most are being somehow lost in the sheer wall of victim's names that never seems to end."

So when politicians say they won't talk about gun control out of respect for victims and their families, it infuriates Ms. Mace. What disregards the families, she said, is not talking about things that can prevent gun violence and not taking any action that could spare other families the pain of losing loved ones. She knows that no single thing will prevent all mass shootings, but she can't help but wonder if her daughter would be alive today if better information sharing about the clearly troubled young man who stormed that lecture hall would have stopped him from getting guns.

Her daughter's death turned Ms. Mace into an advocate for gun-violence prevention. There are times when she has gotten discouraged and disheartened, but she has stayed active in the movement because of the instances of success on the state and local levels of sensible gun protections. While she decries Congress's inaction, she said it may well be the catalyst for change. "By their inaction, they are creating so many more of us," she said.