Frazier Glenn Cross, also known as Glenn Miller, is accused of killing three people Sunday in Kansas City. He allegedly attacked them at a Jewish community center and a Jewish retirement facility. Johnson County, Kan., Sheriff's Office hide caption

itoggle caption Johnson County, Kan., Sheriff's Office

Bob Butler (left) and Bob Gordon paint crosses they placed in front of American flags at Central Christian Disciples of Christ church in the city of Killeen, Texas, which is home to Fort Hood. Joe Raedle/Getty Images hide caption

itoggle caption Joe Raedle/Getty Images

Sgt. First Class Erick Rodriguez stood guard at the entrance to Fort Hood as officials prepared to brief the news media about Wednesday's attack at the post. Erich Schlegel /Reuters/Landov hide caption

itoggle caption Erich Schlegel /Reuters/Landov

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

itoggle caption Eric Thayer/Reuters/Landov

Two people hug early Tuesday after reaching safety outside the Garden State Plaza Mall in Paramus, N.J. A gunman fired several shots there Monday night, sending shoppers and employees scrambling. No one was hurt. Hours later, the suspected gunman's body was found. Police believe he shot himself. Julio Cortez/AP hide caption

itoggle caption Julio Cortez/AP

Workers emerge from a building after a deadly shooting at the Washington Navy Yard on Monday. There are multiple injuries and deaths, and one gunman is dead. Police say they are searching for two other "potential" shooters. Alex Wong/Getty Images hide caption

itoggle caption Alex Wong/Getty Images

Hadiya Pendleton. Courtesy of Pendleton family via the Chicago Tribune /MCT /Landov hide caption

itoggle caption Courtesy of Pendleton family via the Chicago Tribune /MCT /Landov

William Spengler, in an undated image released by the Monroe County (N.Y.) Sheriff's Office. Reuters /Landov hide caption

itoggle caption Reuters /Landov

Jacob Tyler Roberts. Clackamas County (Ore.) Sheriff's Department hide caption

itoggle caption Clackamas County (Ore.) Sheriff's Department

In shock: The scene outside a Minneapolis business Thursday. A gunman killed four people, wounded four others and then killed himself. Richard Tsong-Taatarii/Minneapolis Star Tribune/MCT /Landov hide caption

itoggle caption Richard Tsong-Taatarii/Minneapolis Star Tribune/MCT /Landov