Edward Crawford returns a tear gas canister fired by police who were trying to disperse protesters in Ferguson, Missouri in this August 13, 2014 handout provided by Robert Cohen, St. Louis Post-Dispatch. Four days earlier, unarmed black teenager Michael Brown was shot to death by white police officer Darren Wilson. The killing ignited riots and unrest in the St. Louis area and across the nation. The St. Louis Post-Dispatch received the Pulitzer prize in photography April 20, 2015 for its coverage of the Ferguson, Missouri riots. REUTERS/Robert Cohen/St. Louis Post-Dispatch/Handout via Reuters ATTENTION EDITORS – NO SALES. NO ARCHIVES. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS.