A police officer walks out of the Electrical Engineering Building on the campus of Purdue University in West Lafayette, Ind., Tuesday. One person was killed in a classroom by a gunman who surrendered to a police officer within minutes of the attack, officials said. Michael Conroy/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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Theodore P. Wafer, 54, charged with second-degree murder in the shooting death of Renisha McBride, appears at his arraignment in Dearborn Heights, Mich., on Friday. Paul Sancya/AP hide caption

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Officers on Capitol Hill look at a car following Thursday's shooting, which left Miriam Carey, 34, dead. "We're still very confused as a family why she's not still alive," Carey's sister says. Charles Dharapak/AP hide caption

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Flags fly at half-staff Tuesday after the deadly shootings at the Navy Yard in Washington, D.C. J. Scott Applewhite/AP hide caption

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Kathy Gaarde, one of the people killed in Monday's shootings at Washington's Navy Yard, in a family photo. Her husband, Douglass, says the picture depicts Gaarde "with her 94-year-old mother who she cared for until she passed away last year." Douglass Gaarde hide caption

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President Obama walks out to deliver remarks on the economy at the White House on Monday. At the beginning of his news conference, Obama commented on the shootings at the Navy Yard. Pablo Martinez Monsivais/AP hide caption

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A tribute page to Christopher Lane, an Australian college baseball player who was shot and killed in Oklahoma last week, has drawn thousands of responses on Facebook. Facebook hide caption

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Homicide remains a leading cause of death for young people, even as rates drop. In Chicago, a teenage boy grieves next to a memorial where Ashley Hardmon, 19, was shot and killed on July 2. Gunmen fired while she was chatting with friends. Scott Olson/Getty Images hide caption

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Older men may have guns in the home that can pose a risk when people are depressed or not thinking clearly. iStockphoto.com hide caption

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A young neighbor watches as police respond to a double homicide in Flint, Mich., on June 30. Organizations including the Michigan Youth Violence Prevention Center are working to help young people choose non-violent solutions to conflict. Michelle Tessier/MLIVE.COM /Landov hide caption

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