NEWTOWN, Conn. — A grass-roots group involving several people who lost loved ones in the Newtown school shooting is launching a new campaign to address gun violence, reaching out to parents around the country after seeing its push for new federal legislation fall short in Washington.

The group, Sandy Hook Promise, formed shortly after the Dec. 14 massacre of 26 people at the Sandy Hook Elementary School with the goal of turning the tragedy into a moment of transformation for a horrified nation.