The son-in-law of the elderly couple killed this week in a package bomb explosion at their Tennessee home has been charged in the case, authorities said Thursday evening.

A grand jury returned indictments of felony first-degree murder and felony first-degree premeditated murder against Richard Parker, 49, police said at a press conference. Authorities would not elaborate on how they came to identify him as the suspect, and said he was arrested at his home on Thursday.

It was not immediately clear if Parker, who lived on the same Lebanon property as Jon and Marion Setzer, had a prior criminal record. He was being held in lieu of $1 million bond at the Wilson County Jail Thursday evening, authorities said.

Police said the package was placed at the Setzers' home, not shipped through the mail as originally speculated. Jon Setzer, 74, was killed on Monday when he discovered the package, and his wife, Marion, 72, died late Wednesday from injuries sustained in the blast.

Several papers, notes and magazines were found by investigators in and around the blast area, although it's unclear whether any of them were attached to the device, a spokesman for the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives' Nashville Field Division told

"We're in the process of piecing together those notes," ATF spokesman Michael Knight said. "There were notes and papers and such in the area. We have not determined if those are directly or indirectly associated to the bomb."

An $8,000 reward was still being offered for information that leads to a conviction in the case, police said. Anyone with information is urged to contact authorities at 800-TBI-FIND.'s Joshua Rhett Miller, Karl de Vries and The Associated Press contributed to this report.