Investigators combed through the blackened debris of a central Tennessee home on Tuesday seeking clues to the origin and contents of a package that exploded, killing a man and seriously injuring a woman who lived there.
Jon Setzer, 74, was killed, and Marion Setzer, 72, was seriously injured at about 5 p.m. local time on Monday when the package detonated at their home in Lebanon, Tennessee, about 40 miles east of Nashville.
Authorities did not disclose the relationship of the two victims.
Investigators said on Tuesday they have yet to determine whether the explosion happened inside or outside the house, which was situated in a quiet neighborhood.
The blast, which left a crater, "was sufficient to cause major damage to a solid structure," said Michael Knight, a spokesman for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.
Knight said investigators were sifting through the rubble trying to identify bits of what may have been in the package that caused it to explode.
Marion Setzer was flown by helicopter to the Vanderbilt University Medical Center in Nashville for treatment of her injuries, and authorities said they had not yet had a chance to speak with her.
Knight downplayed early unconfirmed reports that the blast involved the home's mailbox, but he did not rule out that the package may have come through the mail.
"We are looking at the mail as a delivery venue for the item," he said.
Authorities announced an $8,000 reward for information leading to arrest and conviction of a suspect or suspects in the case.
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