Police officers moved quickly to take down a man who allegedly threatened to kill pop star Hilary Duff during her appearance on a Canadian TV show.

Hilary Duff was being interviewed Tuesday by MuchMusic host Leah Miller on Live @ Much when a man in the crowd outside started shouting at the 19-year-old singer and actress.

The unidentified man vowed to kill Duff, prompting several police officers to tackle him. "The cops slammed his face into the pavement," said a witness. "He was bleeding."

The commotion happened just feet away from an outdoor platform where Duff later stood to greet fans who surged forward for autographs and pictures.

It's not the first time the lovely young gal has been involved in a scary indicent. Last November, police in Manhattan Beach, Calif., arrested an 18-year-old, Maksim Miakovsky, for stalking and threatening to kill Duff.

A month earlier, Duff and her then-boyfriend Joel Madden of rock band Good Charlotte filed for restraining orders against Miakovsky and his 50-year-old roommate, David Joseph Klein.

Miakovsky pleaded no contest to the charges in January and was sentenced to 117 days in jail and five years probation.

Duff was in Toronto promoting her third studio CD, Dignity. It's too bad her fans don't have any of it! Seriously. Why the hell are there so many people stalking or wishing harm on Hilary Duff? Hopefully older sister Haylie Duff was there to comfort her.

At the very least, she has a legion of fans who wish her the best every single day. And she's got Lindsay Lohan (and possibly Stavros Niarchos) in her camp.