(CNN) -- Jon and Marion Setzer knew tragic loss and comforted others who suffered the same.
Now friends and family are trying to understand the couple's own tragic end and cope with their personal grief.
The elderly Lebanon, Tennessee, couple was killed by a bomb hidden inside a package. Jon Setzer, who carried the package, was killed immediately by the blast. His wife suffered injuries and died Wednesday at Vanderbilt Hospital. He was 74; she was 72.
The lone suspect, police say, is the couple's son-in-law, Richard Parker, who was arrested Thursday and is being held on a million-dollar bond.
Loss, comfort and dedication were the pillars in the Setzers' lives, those who knew them said.
They were church-going, service-oriented people who were not shy to reach out to others in their time of need.
When the couple were growing their family, a neighbor's dog killed their 3-year-old son, Jon Setzer's former law partner George Cate Jr. told CNN affiliate WZTV.
The incident happened decades ago, but afterward, the couple kept up with news reports and reached out to families that lost children in tragedies.
"If a child was killed anywhere or died in an accident or died of illness, they would immediately go and visit with the parents of that child and share something of what they had gone through with the loss" of their own son, Cate said.
"They have devoted themselves to helping other people," he said.
Jon Setzer had a background in journalism and was working for a Methodist publishing house when he met Cate in the Army Reserve, Cate told WZTV.
Setzer attended law school at night and eventually joined Cate to form a partnership that lasted for 12 years in Nashville.
Marion Setzer was a dental assistant, Cate said.
Jon Setzer began his law career focusing on general civil practice but became interested in wills, estates and living trusts, which would become his specialty.
Living trusts were a new at the time, and Setzer became known for hosting highly touted seminars where he explained what they were, Cate said. The free seminars were a marketing tool that brought many clients to the law firm.
Another CNN affiliate, WTVF, reported that the Setzers moved from Nashville to Lebanon to be closer to their four grandchildren, daughter and the son-in-law who would be charged in their killing.
Jon Setzer and his son-in-law were business partners, the affiliate reported.
Records show that Parker was the owner of a business called Legacy Restorations, but the documents do not mention Setzer. The contracting business -- whose address is the same as Parker's home address -- has less than five employees and has been in operation for 23 years, records show.
After the bombing and Parker's arrest, those who knew the Setzers are struggling for answers.
"They were just sweet people," said the Rev. Mike Ripski, pastor at First United Methodist Church in Lebanon.
"Jon I think qualifies for the adjective of 'erudite,' " Ripski told CNN. "He was articulate, he was knowledgeable, a wonderful teacher of his Sunday school class."
Jon Setzer had been a lay preacher, and he taught children until his health began deteriorating.
Ripski recalls Marion Setzer being at a worship service just this week.
"They're the kind of people that you might describe as being ordinarily extraordinary," the pastor said. "They went about what they did in a quiet way but very effective way."
Ripski also reflected on the loss that the Setzers suffered when their son was killed.
"Instead of their becoming angry or bitter or depressed, that experience -- because they were open to being redeemed by the grace of God -- turned them into the beautiful people that they were, people that so many of us were blessed by," he said.