The advocacy group Stop Handgun Violence updated its billboard along the Massachusetts Turnpike near Fenway Park on Saturday to include 20 small hand prints, representing the children killed at Sandy Hook Elementary School in Newtown, Conn.
"These beautiful children can't have died in vain," said John Rosenthal, the organization's chairman.
Stop Handgun Violence is calling on Congress to enact a new federal assault weapons ban. An earlier law expired in 2004.
"There's no reason why young children should die from gun violence," Rosenthal said. "And the only reason it does happen is because we adults have failed to hold our Congress accountable."
Since the Dec. 14 shooting, which also left seven adults and the gunman dead, some lawmakers have expressed support for a new ban. Sen. Dianne Feinstein, of California, plans to introduce a bill when the new Congress meets in January that would restrict the sale and possession of more than 900 weapons, along with ammunition clips with 10 bullets or more.
Despite that, Rosenthal said he's not optimistic.
"I do not expect anything good to happen unless the Democrats find their backbone and the Republicans find their moral compass and decide that children's lives are more important than their blood money contributions from the NRA," Rosenthal said.
The 252-foot billboard also features a digital tally of the number of children killed by handguns since the 2010 elections.
This program aired on December 22, 2012. The audio for this program is not available.