In a tragic twist, law enforcement has determined that the culprit behind the murder of a Tennessee couple may actually have been their own son-in-law.

CNN reports that an investigation by police resulted in the arrest of 49-year-old Richard Parker. Parker has been charged with two counts of felony first-degree murder and two counts of felony premeditated murder.

The victims were 74-year-old Jon Setzer and his 72-year-old wife Marion Setzer. The retired lawyer was killed on Monday when the package bomb that Parker is alleged to have created detonated just inside the Lebanon home he shared with his wife. Setzer did not survive the blast, but his wife Marion was rushed to Vanderbilt Hospital. She died Wednesday evening.

According to Wilson County Sheriff Robert Bryan, Parker lived next door to his in-laws. Bryan stated that Parker was the sole suspect, however nothing was revealed regarding a possible motive or even what evidence led investigators to suspect him in the first place.

Officials did reveal that a note was found among the debris that may have been connected to the bomb. The contents of the note and whether or not it matched Parker’s own handwriting has not yet been determined.

Tennessee bombing suspect who 'killed wife's parents' ran company with father-in-law via @DailyMailUK http://t.co/2k89ryHxM5

— Chris (@Chris_1791) February 15, 2014

How Horribly Sad for Their Daughter! “@JosephBrandon8: Son-in-law charged in fatal Tennessee package bombing http://t.co/sN1jy3NQHO”

— Bonnie Cozzetto (@COZZEB) February 14, 2014

Bryan did say of of the case that, “right now we feel like we have the person responsible for committing this crime in custody.”

Those who knew the victims are still struggling with feelings of shock and disbelief over the murder.

Ken Caldwell, a friend of the family couldn’t understand how the bombing was “targeted” as investigators believe. While speaking with WTVF about the murder Caldwell said, “When I’ve heard it said that it was targeted, I thought, well, they must have targeted the wrong person.”

The Tennessee Bureau of Investigation revealed that Parker was convicted of arson in 1993. He served four years on probation.

TBI director Mark Gwyn says Parker is being held on a $1 million bond.

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