Relatives of victims of gun violence attend a press conference honoring the second anniversary of the Sandy Hook Elementary School shootings in Washington, D.C. on Dec. 10, 2014. Saul Loeb/AFP/Getty Images hide caption

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Two Years Later, Still Learning From Sandy Hook
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Richard Martinez, whose son Christopher Michael-Martinez was killed in Friday's mass shooting in Isla Vista, Calif., breaks down as he talks to media outside the Santa Barbara County Sheriff's headquarters on Saturday. Jae C. Hong/AP hide caption

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Flowers, candles and stuffed animals at a makeshift memorial in Newtown, Conn., the week after 20 children and 6 adults were killed at Sandy Hook Elementary School. Eric Thayer/Reuters/Landov hide caption

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Former Rep. Gabby Giffords and her husband, Mark Kelly, at a gun show in Saratoga Springs, N.Y., in October. Giffords was shot in the head in a 2011 mass shooting in Tucson. She and Kelly have since founded a political action committee to push for tougher gun laws. Tim Roske/AP hide caption

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An image from a Connecticut State Police report on the shootings at Sandy Hook Elementary School shows a scene at 36 Yogananda St. in Newtown, Conn., where Adam Lanza killed his mother before driving to the school and killing 26 students and staff last December. AP hide caption

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Voters in Newtown, Conn., have approved a plan to use nearly $50 million in state funds to demolish Sandy Hook Elementary and build a new school in its place. This photo provided by Craig Hoekenga shows his son Trey, a kindergarten student at Sandy Hook, on the school bus this year. The window has a quote from the late principal, Dawn Hochsprung, who was killed in last December's mass shooting. Craig Hoekenga/AP hide caption

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Francine Wheeler, seen here delivering the presidential address alongside her husband, David, urged the Senate to pass gun control legislation. YouTube hide caption

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Early Thursday morning, a school bus carrying students from Sandy Hook Elementary headed to their new school. Timothy A. Clary/AFP/Getty Images hide caption

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Jean Cochran reporting on the NPR Newscast
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Remembering the victims: Earlier this month, two mourners paused at a makeshift memorial in Newtown, Conn., for the children and adults killed at Sandy Hook Elementary School. Zhang Chuanshi /Xinhua /Landov hide caption

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People visit a memorial outside Sandy Hook Elementary School in Newtown, Conn., on Dec. 15. Spencer Platt/Getty Images hide caption

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Shootings Leave Sandy Hook Survivors Rethinking The Odds
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A person's DNA can say a lot about a person, but not why someone has committed a horrific crime like mass murder. iStockphoto.com hide caption

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Killer's DNA Won't Explain His Crime
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A child peers through firefighters standing as the procession heads to the cemetery outside the funeral for school shooting victim Daniel Barden at St. Rose of Lima Catholic Church in Newtown, Conn., Charles Krupa/AP hide caption

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In Newtown: A memorial to the victims. Mario Tama/Getty Images hide caption

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NPR's Don Gonyea, reporting on 'Morning Edition'
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