"Trump is going to be no more Mr. Nice Guy," Republican presidential nominee Donald Trump said Friday to a Colorado rally audience chanting to lock up rival Hillary Clinton.

"You know what, I'm starting to agree with you. ... Every time I mention her, everyone screams, 'Lock her up, lock her up,'" Trump said.

In early July, the FBI director recommended against charges for Clinton's use of a private email server during her time as secretary of state.

Trump has been quick to highlight Clinton's email scandal in the past but has shied away from agreeing with the audience's call to put Clinton behind bars. But this time, he appeared to go off script.

"Isn't it better when we don't have these teleprompters?" Trump said.