Donald Marshall is a geophysicist, not an expert on criminal law or public safety. But after the mass shooting at a Newtown, Conn., elementary school two months ago, the grief he saw in his own town of Bedford stirred him to action.

“I read about a gun buyback program in Camden, New Jersey, and it struck me that maybe we could do the same thing here,” said the longtime resident. “It’s a small thing we could do.”