KNOX CITY, MO. (AP) -- A brother and sister face murder charges in the 2006 killing of a 57-year-old northeast Missouri man.

Larry Callahan was shot to death during a robbery at his home in Knox City last October. Now, 28-year-old Shane Colby Roberts is charged with first-degree murder. His 27-year-old sister, Angela Knowles, is charged with second-degree murder.

Both were already in the Adair County Jail after their arrest last week following a multi-county investigation into a string of burglaries, thefts and arson. Roberts lives in Kirksville, Knowles in Greentop.

Investigators say Knowles told them her brother kept a shotgun shell from the killing "as a souvenir." The Missouri State Highway Patrol says the shell has been recovered.

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