A woman convicted in a bizarre Pennsylvania bank robbery plot that left a pizza delivery driver dead when a bomb strapped to his neck exploded has died in prison.

The U.S. attorney's office in Pittsburgh says the federal Bureau of Prisons confirms 68-year-old Marjorie Diehl-Armstrong died Tuesday at the Federal Medical Center in Carswell, Texas. An office spokeswoman says she doesn't know the cause of the inmate's death.

Diehl-Armstrong was serving a life sentence plus 30 years in the 2003 Erie bank robbery plot. The plot ended in the death of 46-year-old Brian Wells when a bomb locked to his neck exploded following the robbery.

Authorities alleged Diehl-Armstrong instigated the plot and later killed a co-conspirator. A federal appeals court last year rejected her bid for a new trial.