(Oak Park Heights, MN)  —  Donald Blom, who was serving a life sentence for the 1999 murder of Moose Lake convenience store worker Katie Poirier, died Tuesday at the state prison in Oak Park Heights.  The Star Tribune reports a state Corrections Department spokesperson says it was “an expected natural-causes death due to illness.”  Poirier, who was 19 years old, was kidnapped from the store where she was working alone just before midnight on May 26th, 1999.  Her body was never recovered, but a tooth with dental work matching Poirier’s plus burned human remains were found on Blom’s property.  He confessed to authorities and later tried to withdraw it.