Leona Lewis was punched in the temple by a so-called fan who waited for more than five hours in line to meet her at a London book singing Wednesday, where the 24-year-old singer was signing copies of her new autobiography, Dreams.
Fans at the scene described the scary incident to the UK Sun.
"It was horrendous," Emily Rose, who was standing behind him, told the paper. "He waited for Leona to bow her head then just lashed out -- a proper full-on punch on the side of her face. She let out a piercing scream and grabbed her temple. Security piled on this guy and Leona just started running."
Fan Steve Caris described Lewis' creepy attacker.
"This bloke looked like a nutcase," Caris told the Sun. "He was like a bumpkin, well over 6ft tall and with buck teeth. He really walloped Leona. She must have been in agony."
Lewis was taken to London's Harley Street Hospital after the attack, and reports indicated she suffered bruising.
Scotland Yard said an arrest has been made in connection with the attack.
Lewis shot to prominence as the winner of the 2006 X Factor Competition; she was recently featured on the VH1 Divas special, where she collaborated with 80s star Cyndi Lauper on a cover of the Lauper's hit single, True Colors.