BOSTON (CBS) – Twenty small handprints have been added to the 252-foot anti-gun violence billboard along the Massachusetts Turnpike.

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Stop Handgun Violence, which pays for the billboard, says it added the handprints to represent each child killed in the Sandy Hook Elementary school massacre.

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The billboard, which has stretched alongside the Mass Pike for years, calls for a ban on military assault weapons and high capacity ammunition clips and criminal background checks for gun sales.

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According to the organization behind the billboard, an average of 83 Americans are killed by guns each day.