NEWTOWN, Conn. — Nicole Hockley says she still finds herself reaching for her son’s hand or expecting him to crawl into bed with her for a hug before school.

“It’s so hard to believe he’s gone,” said Hockley, whose son Dylan was among the 20 first-graders and six adults killed by a gunman a month ago at Sandy Hook Elementary School.

She was among several parents to speak Monday at the launch of Sandy Hook Promise, a group calling for a national dialogue to help prevent similar tragedies. Parents held photographs of their children, spoke in wavering voices, cried and hugged.

“I do not want to be someone sharing my experience and consoling another parent next time. I do not want there to be a next time,” Hockley said.

The group did not offer specific remedies, saying it wants to have open-minded discussions about a range of issues, including guns, mental health and safety in schools and other public places. Several speakers said they did not believe there was a single solution.

“We want the Sandy Hook school shootings to be recalled as the turning point where we brought our community and communities across the nation together and set a real course for change,” said group co-founder Tom Bittman.

Adam Lanza, 20, shot his way into the school on Dec. 14 and killed 26 before committing suicide as police arrived. He also killed his mother at their Newtown home.

Jeremy Richman, whose daughter Avielle was killed, said a deeper understanding of mental health issues is essential. He and his wife, Jennifer Hensel, started a foundation to explore issues such as risk factors and successful interventions.