Law Abiding Citizen - Cell Phone Scene

------Hello? *SPLAT*

The best death scene from the 2009 film Law Abiding Citizen. Judge Burch's demise was the most abrupt and satisfying. But what exactly was it that killed her? IMDB's parental guide says, "A woman is shot in the head." Meaning it was a cell phone gun that killed her. A phone that fires a single bullet when a call is received. But, other sites like Cinemorgue and Wikipedia say it was a bomb that killed her. Her phone being rigged by Shelton(Gerard Butler) to explode when she answers it. Whatever the cause, she should have let it go to voicemail.