NEWTOWN, Conn.—Exactly a month after the massacre at Sandy Hook Elementary School, dozens of teary-eyed family members, many clutching framed photos of their slain children, gathered in the basement of the town hall on Main Street to announce the launch of Sandy Hook Promise. The group's mission is to promote a national dialogue on gun violence, mental health and school safety—and to honor the 26 school shooting victims with a promise of "real change."

About 30 family members took their seats on a small stage underneath a basketball hoop at one end of the Edmond Town Hall gym for an emotional press conference attended by friends, community leaders, first responders and about 150 members of the media. Many wore green-and-white ribbons. Some held hands as tears streamed down their faces. Tissue boxes were placed at their feet.

Nicole Hockley, whose 6-year-old son Dylan was killed, was the first parent to speak.

"It's a sad honor to be here today," Hockley said, her voice occasionally cracking as she spoke. "At times it feels like only yesterday, and at others it feels like many years have passed. I expect him to crawl into bed beside me for early morning cuddles before school. It's so hard to believe he's gone."

"I'm Ana's mom," Nelba Márquez-Greene, whose 6-year-old was killed in the Dec. 14 shooting, said. "A month ago I put two children on the bus, and only one came home.

"We choose love, belief and hope instead of anger," she continued. "We choose love. Love wins. Love wins in Newtown. This is a promise to do everything in our power to be remembered not as the town filled with grief and victims but as a place where real change began," Márquez-Greene said.

"Doing nothing is no longer an option," noted Tom Bittman, co-founder of the initiative and a resident whose children once attended Sandy Hook School. "We want to Newtown to be remembered for change, not tragedy."

[Related: Scenes from Newtown, Dec. 14-21, 2012]

"My wife and I have spent the last month tasked with being the best possible parents for our surviving son, Nate," David Wheeler, whose son Ben was among the 20 first-graders killed, said. "But what we have recently come to realize is that we are not done being the best parents we can be for Ben. If there is something in our society that needs to be fixed or healed or resolved, it needs a point of origin. It needs parents."

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Wheeler asked parents to begin the process of change by looking inward: "I would respectfully ask every parent that hears these words to pause and ask yourself, 'What is it worth to you? What is worth doing to keep your children safe?'"

Speakers urged supporters to sign the Sandy Hook Promise and to begin a dialogue "to identify and implement holistic, common-sense solutions that will make our community and our country safer from similar acts of violence."

The group stopped short of responding directly to the National Rifle Association, which said on Sunday that it has enough support in Congress to block any new gun-control laws. "We do not have any response to that," Tim Makris, another co-founder of the initiative, said. "We need to take the time to have a national discussion."

"Some of us are gun owners," Bittman said. "We hunt, target shoot, protect our homes. We teach our sons and daughters how to use guns safely. [But] we're not afraid of a discussion about responsibility and accountability. The bottom line is we must act. We can't let this happen again."

"There is not going to be one simple solution," Jeremy Richman, father of 6-year-old victim Avielle Richman, said. He added that he and his wife have started a foundation in Avielle's honor to study "behavioral and biochemical mental health."

One thing is clear, Makris said: "We need to do something different."