The December shooting massacre at Sandy Hook Elementary in Newtown, Conn., revived a national debate about gun violence. It's one that's emotional and often highly personal, and it's happening in places far from the halls of Congress. Earlier this week, President Obama was in Minneapolis advocating new limits on guns; no law or set of laws, he said, can keep children completely safe. NPR's David Welna was there for the visit and sent this reporter's notebook about the voices he encountered.