Francine Wheeler, whose 6-year-old son, Ben, was killed inside Sandy Hook Elementary School, stepped in for President Barack Obama to deliver the president's weekly radio and Internet address. She is the first person to deliver the address other than Obama or Vice President Joe Biden since the two took office in 2009.
"Thousands of other families across the United States are also drowning in our grief," Wheeler said in the address.
"Please help us do something before our tragedy becomes your tragedy."
Her husband, David Wheeler, sat silently next to her as she made the recording in the White House Library. Both wore the small green pins that have become a symbol of the December schoolhouse shooting that killed 20 first-graders and six adults.
Obama asked Wheeler to deliver this week's address, which was taped Friday and released on Saturday. The White House said Wheeler and her husband wrote the remarks themselves.
"Sometimes, I close my eyes and all I can remember is that awful day waiting at the Sandy Hook Volunteer Firehouse for the boy who would never come home - the same firehouse that was home to Ben's Tiger Scout Den 6," Francine Wheeler said. "But other times, I feel Ben's presence filling me with courage for what I have to do, for him and all the others taken from us so violently and too soon."
Some of the Sandy Hook families, with Obama's blessing, have launched a stepped-up effort to push a gun control bill through Congress.
As the fate of the legislation appeared uncertain last week, Obama traveled to Hartford, Connecticut - about an hour's drive from Newtown - to make his case for the legislation. On the return trip to Washington, he brought back 12 of the victims' family members, who have been meeting with senators.
The Senate is considering a Democratic bill backed by Obama that would expand background checks, strengthen laws against illegal gun trafficking and slightly increase school security aid. The bill passed its first hurdle on Thursday, and senators will vote on amendments to the bill next week. Its fate in the Republican-controlled House is uncertain.
Shortly after the vote on Thursday, White House spokesman Jay Carney said the voices of the Newtown families may have been the decisive factor.
The bill before the Senate stops well short of Obama's call to ban assault rifles and the high capacity magazines that leave shooters able to fire large bursts of ammunition without having to reload.
It would subject almost all gun buyers to background checks, stiffen federal laws barring illicit firearms sales and provide slightly more money for school safety measures. Background checks are aimed at preventing criminals and mentally ill people from getting weapons, and gun control advocates consider broadening the system to be the most effective step available to lawmakers.
Opponents including the National Rifle Association, a gun advocacy group, say the measures would infringe on the constitutional right to bear arms and inconvenience law-abiding citizens while being easy for criminals to evade.