Ben Carson -- I Used to Outrun Cops Before They Shot You ... JK!! (VIDEO)

Ben Carson flashed some energy and personality on the campaign trail Wednesday ... by cracking a joke about cops shooting black kids.

The good doctor was stumping in New Hampshire, and reliving his childhood -- telling a story about how he and pals used to throw rocks at cars and run from the police.

Innocent enough tale about his wayward youth, and then he said ... "That was back in the day before they would shoot you."

Hard to tell if the GOP presidential candidate's comment was truly off-the-cuff or planned, but considering the current climate ... it seems like a risky door to open.

Especially for a guy who's moving up in the polls.