Villaume said the Benekes are seeking substantial damages. Beneke, 34, left behind his parents, a wife and a young son. The family was not conducting media interviews Friday.
Messages left with Accent Signage and with the attorney handling Engeldinger's estate were not immediately returned.
Villaume said the lawsuit is important, especially given recent attacks like the one in Newtown, Conn., in which 20 elementary school students were gunned down.
"It's about time that people step up and speak out against gun rights," he said. "Guns in the hands of dangerous people are a dangerous thing, and they kill and harm and maim innocent people — and that's what happened here."
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