National Guard troops stand watch along E. Pratt St. in Baltimore, Maryland April 28, 2015. U.S. President Obama on Tuesday said rioting in Baltimore emphasized the need for national "soul searching" on the way police forces deal with the public. Obama, in his first public statement about Freddie Gray, a Maryland black man who died of a broken spine after being arrested, said such cases are not new. (REUTERS/Eric Thayer)