Raleigh, North Carolina (CNN) Donald Trump on Tuesday night repeatedly hammered his message that there is a "rigged system" at work, pointing specifically to the FBI decision to not recommend criminal charges against Hillary Clinton for her use of email while serving as secretary of state.

Trump seized on the FBI's decision as he addressed the crowd of fervent supporters in this potential battleground state, calling it the "best evidence ever that we've seen that our system is totally rigged."

He accused Clinton, the presumptive Democratic nominee, of bribing the U.S. attorney general -- offering little to back up the dramatic accusation. And he called the FBI's decision, announced earlier Tuesday by the agency's director James Comey, a "tragedy."

"Everybody thought based on what was being said she was guilty. She was guilty. And it turned out that we're not going to press charges. It's really amazing," Trump said as his crowd of more than 2,200, according to the theater, erupted in a chorus of boos.

"We have a rigged system, folks," he added.

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