KIMBALL, Minn. – Nearly 40 years have passed since a central Minnesota Postmaster was killed when a bomb exploded as he sorted packages.

Kimball Postmaster Ivend Holen was killed on May 13, 1976 when a package exploding while he sorted mail.
Forty years, and yet interest in the case… and determination to find the person responsible… has not waned.
On Thursday the U.S. Postal Inspection Service officially announced a $100,000 reward for information that leads to the arrest and conviction of the person who mailed the bomb that killed Kimball Postal Inspector Ivend HolenĀ on May 13, 1976. While investigators believe Holen was not the target of the bomb, that does not change the fact that it exploded and ended his life.
source: $100K reward offered in fatal postal bombing