Tennessee authorities have announced an arrest in the package bomb that took the life of a retired lawyer on Monday and later caused the death of his wife on Wednesday night in Lebanon, Tennessee.

It is reported that their investigation of the bomb that was placed outside the home of Jon and Marion Setzer, determined that the man responsible for the bomb was none other then their son-in-law, 49-year-old Richard Parker.

It was announced at a press conference earlier today that a Grand Jury had handed down an indictment against Parker.

Parker was arrested on two counts of felony premeditated murder at his home on Thursday and his bail was set at $1 million. Authorities have not released a motive for the killing of the retired couple. Wilson County Sheriff, Robert Bryan stated that Parker lived next door to the lawyer and his wife. They are releasing very little information at this point.

When investigators sifted through the debris at the home of 74-year-old Jon and 72-year-old Marion, they found bits and pieces of paper comprising notes and magazines at the scene. They stated earlier in the investigation that they felt those scraps held crucial evidence in the case. “This is a very important piece of evidence, because now you may have handwriting,” said former ATF agent and bomb expert Joseph Vince. They did not divulge what information or evidence led them to arrest Parker however.

It is believed by authorities, that Setzer picked up the package from a location about 200 yards from his home and took it to his house. Once inside his house, apparently the package was opened as his wife looked on. The powerful blast blew out windows throughout the first floor of the two-story brick house. Jon was killed instantly and declared deceased at the scene, Marion lingered for two days after she was airlifted to Vanderbilt University Medical Center.

Authorities earlier in the investigation were not sure if the package had been delivered through the mail, but they have sinced ruled that out and state that the package was placed at the location by Parker.

Currently, Parker is the only suspect in the investigation.