Sanford, Fla., police Officer Timothy Smith holds up the gun that was used to kill Trayvon Martin, while testifying on June 28, 2013, the 15th day of George Zimmerman's murder trial. Zimmerman has listed the gun for sale online. Pool/Getty Images hide caption
Former Florida Gov. Jeb Bush takes the stage to formally join the race for president Monday at Miami Dade College in Miami. David Goldman/AP hide caption
Dr. Martin Luther King Jr., marches with other civil rights protesters during the 1963 March on Washington. AP hide caption
A booking photo provided by the Seminole County Public Affairs shows George Zimmerman on Saturday, Jan. 10, 2015. In the latest in a string of run-ins with the law in the past two years, Zimmerman has been charged with aggravated assault. AP hide caption
Lawyer Bruce Zimet comforts Marissa Alexander during a hearing Monday in Jacksonville, Fla. Bruce Lipsky/AP hide caption
George Zimmerman. Gary W. Green/EPA/LANDOV hide caption
Shellie Zimmerman in court on June 20. Gary W. Green/UPI/Landov hide caption
George Zimmerman "probably feared for his life," juror B37 told CNN. Gary W. Green/EPA/LANDOV hide caption
Protesters in support of Trayvon Martin march across the Brooklyn Bridge after attending a rally organized by the Rev. Al Sharpton on Sunday in New York City. Andrew Burton/Getty Images hide caption
President Obama tackled race head-on in his first on-camera response to George Zimmerman's acquittal in the shooting death of Florida teenager Trayvon Martin. Carolyn Kaster/AP hide caption
President Obama during his appearance at the White House on Friday. Saul Loeb /AFP/Getty Images hide caption
President Obama at the White House on Friday, as he spoke about the death of Trayvon Martin and the national discussion that the case has generated. Larry Downing /Reuters /Landov hide caption
Sybrina Fulton, the mother of Trayvon Martin, appears for an interview with NPR's Michel Martin at Tell Me More. Doriane Raiman/NPR hide caption
George Zimmerman "probably feared for his life," juror B37 told CNN. Gary W. Green/EPA/LANDOV hide caption
Attorney General Eric Holder speaks at the annual convention of the NAACP in Orlando, Fla., on Tuesday. Holder told the convention that "Stand Your Ground" laws that have been adopted in 30 states should be reconsidered. David Manning/Reuters /Landov hide caption