Prison officials say 40-year-old David Langlet was found unresponsive in his cell last Friday.
Langlet had been behind bars since December following his conviction for the June 12, 2000 targeted shooting of 27-year-old Shane Preece.
Surrey RCMP reopened the cold case last year and arrested and charged Langlet in October.
Prison officials have not said what caused his death.
A release from Kent Institution in Agassiz, B.C., says police and the coroner have been notified, and Correctional Service Canada will review the circumstances of the death.