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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Community members and students from Marysville-Pilchuck High School gather for a vigil at the Grove Church in Marysville, Wash., Friday night. Two students died in the violence, including the gunman. Several more were wounded. David Ryder/Getty Images hide caption

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People react as they wait at a church on Friday where students were taken to be reunited with parents following a shooting at Marysville Pilchuck High School in Marysville, Wash. Ted S. Warren/AP hide caption

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Freshman Hailee Siebert, 15, cries on her mother's shoulder after a shooting on Tuesday at Reynolds High School in Troutdale, Ore. The gunman has been identified as 15-year-old student Jared Michael Padgett. Rick Bowmer/AP hide caption

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This image provided by the Orangeburg-Calhoun Regional Detention Center shows Justin Bernard Singleton, 19, of Charleston, who is charged with murder in the death of university student Brandon Robinson. Uncredited/AP hide caption

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Arapahoe County Sheriff Grayson Robinson holds a picture of Claire Davis, 17, at a briefing at Arapahoe High School in Centennial, Colo., the day after the Dec. 13 shooting. Davis died Saturday. Ed Andrieski/AP hide caption

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