Public memorials, like the one at the scene where Freddie Gray was arrested, have become sites to commemorate other deaths of unarmed black men in similar police encounters across the country. David Goldman/AP hide caption

itoggle caption David Goldman/AP

Canadian-born Omar Khadr is seen in a courtroom sketch during a 2010 hearing at the U.S. military prison at Guantanamo Bay, Cuba. He was moved to a Canadian prison in 2012. Janet Hamlin/AP hide caption

itoggle caption Janet Hamlin/AP

New York Mayor Bill de Blasio (center), City Police Commissioner William Bratton (second from right) and other NYPD officers address a news conference on Jan. 5. There is debate surrounding the citywide increase of low-level crime enforcement, otherwise known as the broken windows approach to policing. Richard Drew/AP hide caption

itoggle caption Richard Drew/AP

Marilyn Mosby, Baltimore's prosecutor, announced criminal charges against all six officers suspended after Freddie Gray suffered a fatal spinal injury while in police custody. Alex Brandon/AP hide caption

itoggle caption Alex Brandon/AP