Bewildered residents in rural Tennessee are grappling with fear and confusion as they try to understand why someone would send a bomb in the mail to their neighbor.
Retired lawyer John Setzer, 74, died Monday after "an unknown package exploded," the Tennessee Bureau of Investigation said.
His wife, 72-year-old Marion Setzer, was seriously injured and airlifted to Vanderbilt University Medical Center.
A barrage of federal, state and local authorities descended on the neighborhood near Lebanon, Tennessee, about 30 miles east of Nashville. The FBI, U.S. postal inspectors, the Department of Homeland Security and the Bureau of Alcohol, Tobacco, Firearms and Explosives are also investigating.
So far, they haven't publicly disclosed a motive. Those who knew the couple well are astonished.
"It doesn't make sense at all," family friend Ken Caldwell told CNN affiliate WTVF. "When I've heard it said that it was targeted, I thought, well, they must have targeted the wrong person."