NASHVILLE, Tenn. (AP) - A preliminary autopsy report has found that Byron Looper, a Tennessee inmate serving a life sentence for the murder of state Sen. Tommy Burks, died in his cell this week of a "heart event."

The Chattanooga Times Free Press reports that Looper's family has requested an independent autopsy.

Tennessee Bureau of Investigation spokeswoman Kristin Helm says agents haven't ruled out foul play in the case. She says the death investigation will proceed until the final autopsy report is completed and then will be turned over to the district attorney's office.

Looper was convicted of murder in the Oct. 19, 1998, fatal shooting of Burks while he sat in his pickup truck near his Cumberland County farm. Looper was running as a Republican against Burks for the state senate seat.

Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.