Via ThinkProgress, here's video of Virginia shooting victim Alison Parker's father Andy emotionally promising that he will campaign for laws that keep handguns out of the possession of unstable and potentially violent individuals.
"We’ve got to do something about crazy people getting guns," Parker says. "My mission in life… I’m going to do something to shame legislators into doing something about closing loopholes and background checks and making sure crazy people don’t get guns."
Parker's position is a familiar one at this point. Here's what Richard Martinez, a California attorney, said when his son was shot to death in a random attack by Elliot Rodger in 2014:
“I don’t care about your sympathy. I don’t give a shit that you feel sorry for me. Get to work and do something. I’ll tell the president the same thing if he calls me. Getting a call from a politician doesn’t impress me ... Today, I’m going to ask every person I can find to send a postcard to every politician they can think of with three words on it: ‘Not one more.’ People are looking for something to do. I’m asking people to stand up for something. Enough is enough.”
From a New York Times story about the families of the individuals murdered by heavily armed Colorado shooter James Holmes in 2012:
“Our former life is now in our rearview mirror,” Sandy Phillips wrote on Facebook as she and her husband, Lonnie, locked the door of their San Antonio home and steered their new camper north, toward Colorado and the trial of the man who killed their daughter, Jessica Ghawi ... the Phillipses have traveled the country, arguing for gun control and background checks, unsuccessfully trying to sue ammunition manufacturers, and telling stories about Ms. Ghawi, a 24-year-old budding sports reporter.
Mark Barden's 7-year-old son Daniel was murdered by Adam Lanza at Sandy Hook Elementary in 2012. From the New Haven Register:
"What would really hurt would be if people forgot about it" and returned to their normal lives and let the issue — changes in society to make some future Dec. 14 less likely to occur — fade away, [Barden] said. "If this doesn't do it, I don't know what will."
Going further back, former Rep. Carolyn McCarthy's husband was murdered in a mass shooting on the Long Island Rail Road in 1993, after which she ran for Congress. Here's a USA Today article about her from Jan. 2015:
Early in her congressional career, Carolyn McCarthy's plea – rare in politics – was, "Let me go home!'' That is, pass gun control laws and let me retire, having done what I came to Washington to do. Now, after 18 years, she finally is going home ... But she goes home having accomplished almost none of what she hoped to accomplish when she first ran as a gun control advocate.
It's still legal in most states to buy a gun from a private dealer without being subject to a background check, while even background checks on regulated purchases can fail to identify individuals who should be denied guns because sellers are allowed to go forward if the check hasn't been completed in three days.