Jasmine Nguyen of Anaheim was at the home of Earl Decastro with her mother and 7-year-old sister for a party in the 8000 block of Cornflower Circle, near the intersection of La Palma and Stanton avenues, prosecutors said.
Decastro is accused of igniting fireworks in front of his home for more than an hour before setting off an illegal $400 firework in the shape of a cake as a "grand finale," prosecutors said.
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The firework "malfunctioned" and exploded aerial mortar shells into the driveway where his guests were watching the display, prosecutors said.
As some of his guests dashed into Decastro's home to escape the mortars, a stash of fireworks near Jasmine exploded, prosecutors said. Jasmine was rushed to UCI Medical Center where she was later pronounced dead, prosecutors said.
Decastro was charged with involuntary manslaughter, unlawfully causing a fire with great bodily injury and possessing dangerous fireworks in excess of 100 pounds, all felonies.