The son-in-law of a Tennessee couple who was killed after a bombing at their home Monday in Wilson County was arrested and charged with their deaths on Thursday.

Richard Parker, 49, is facing two counts of first-degree murder, two counts of premeditated first-degree murder and a count of unlawful possession of a prohibited weapon for the bombing that killed his in-laws, Jon and Marion Setzer, the Tennessean reported. Jon Setzer, 74, died at the scene on Monday while Marion Setzer, 72, died at a local hospital on Wednesday, according to the newspaper.

The Setzers were fixtures at the First United Methodist Church, where Jon occasionally taught Sunday school and Marion was involved with a ministry. The church’s senior pastor called the Setzer’s “wonderful people.”

“The grief is deep [and] profound because they were such wonderful people.” the Rev. Mike Ripski said. “They lived out their faith. Two people targeted for this kind of violence doesn’t make sense at all.”

Wilson County Sheriff Robert Bryan made the announcement of Parker’s arrest at a news conference on Thursday. Bryan said the sheriff’s office, the Tennessee Bureau of Investigation, the FBI, the Bureau of Alcohol, Tobacco, Firearms and Explosives as well as local law enforcement aided in the investigation that led to Parker being arrested and charged with the murders of the Setzers.

"The collaborate efforts of all these agencies and hundreds of individuals working tirelessly throughout the past few nights has resulted in the arrest of the person responsible for this crime," Bryan said, according to local CNN-affiliate WTVF.

Parker was arrested at his home, which is behind the Setzers’ residence but shares a driveway. His bail was set at $1 million. Parker couldn’t make bail and was booked into the Wilson County Jail.

The Tennessee bombing suspect has a prior criminal record, according to the Tennessean. He was convicted for arson in 1993 and served four years’ probation for the crime.

Despite Thursday’s arrest, the investigation into the Tennessee bombing is still ongoing, Jeff Fulton, the ATF special agent in charge for the agency’s Nashville office, said. Fulton said there's an $8,000 reward for anyone who provides information that leads to a conviction in the case.

"There is still evidence being examined at TBI's lab and the ATF's lab," he said. Fulton added that the bomb was placed at the home and wasn’t mailed or delivered through a courier.

The sheriff’s office received calls about an explosion at the home around 5 p.m. Monday. When authorities arrived on the scene, they found Jon Setzer dead. Marion Setzer was airlifted to Vanderbilt Hospital, according to a TBI press release.

Anyone with information on the Tennessee bombing was urged to call the TBI at 1-800-TBI-FIND.