A police spokesperson claims the Canadian was "horsing around with members of his staff" before his sold-out gig at the Maryland State Fair, and hurled the water balloons at two officers who were controlling the crowds.
One of the balloons hit a cop's gun belt and burst, while another balloon bounced off the other trooper.
ENews reports that Bieber then retreated to his trailer while his bodyguard successfully persuaded the officer not to put a black mark on the kid's squeaky-clean record (not including the madness that ensues among his fans when his very name is mentioned).
The officers decided not to write up a report, but the police representative has deemed the "Baby" hitmaker's actions "inappropriate behavior."
But it looks like Bieber wouldn't have changed anything that happened that day. He tweeted: "Still laughing. GREAT DAY" later that night.