Trump made the remarks in an interview with Bill O’Reilly. When O’Reilly said that “Putin’s a killer,” Trump likened the United States to Russia and its human rights violations, replying that “there are a lot of killers. You think our country’s so innocent?”

USA Today – Trump says America isn’t so innocent
NBC News – Trump, Challenged About Putin, Says ‘Our Country’s So Innocent?’
CNN – Trump defends Putin: ‘You think our country’s so innocent?’