KIMBALL, Minn. (WCCO) — Federal investigators say they’re making new progress in trying to find who’s responsible for a bombing in Minnesota more than three decades ago.

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“We want this solved, yes,” said Postal Inspector Virginia Lalley. “It’s for Ivend Holen’s family, for all postal employees, for the Postal Service. It’s been out there too long.”

She’s one of two postal inspectors in St. Paul who are assigned to the bombing of the post office in Kimball, Minn., about an hour-and-a-half northwest of the Twin Cities in Stearns County.

Ivend Holen died soon after the bomb exploded in 1976. He was sorting mail before the post office opened and was blown out a metal door. He died on the way to the hospital.

“I would liken it to a sonic boom, but louder,” Kimball resident Maxine Doran said.

Doran was at home when that bomb blew apart the town’s post office. She rushed to see what had happened on Main Street.

“What I remember is the upper glass being broken,” she said about the front windows of the post office. “I think all the glass was broken.”

She also remembers detectives descending on Kimball, and the dead too, including her friend, Holen.

“Oh, it was unsettling,” she said.

Pain overshadowed the pleasant way of life many residents knew in central Minnesota. And for some, it’s a point in time that still feels like yesterday. Doran recalls suspicion blanketing Kimball back then, because no one knew who sent the package and why.

Packages were sorted based on where they would be delivered in town. This one was in the pile for Route 1. But postal inspectors cannot be certain if it was actually meant for someone living off Route 1, or if it as meant for someone else, possibly Holen himself.

“It was so tragic,” recalled Jennifer Harriel, Holen’s granddaughter. “It was something that was somebody else’s choice, and it was intentional.”

She called him a loving and caring man. Holen was a veteran of World War II, a Kimball American Legion Officer, and was involved in his community and close to his family.

“There are a lot of people who would have benefited greatly from meeting Grandpa,” she said.

Lalley called the case “intriguing,” and she has been tracking down leads and tips in the case since being assigned to it five years ago. Even she admits that it’s tough.

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“Pretty powerful bomb,” she said while showing pictures police took of the crime scene for the first time. “Obviously meant to kill someone.”

A fire followed the explosion at 6:42 a.m. Inspector Lalley believes that it’s now time to also show something else federal investigators have never shown before.

It’s been widely known that a tackle box housed the bomb, but no one except inspectors and detectives have seen what it looks like.

“We’ve been kind of holding that close to our vest here,” she said.

Lalley’s exact replica of the tackle box is pea green, made of metal and is only about a foot long, and a couple of inches wide.

“I think it was a fairly common tackle box at the time,” she said.

It bears the name “Old Pal” at the top, along with a picture of a fish.

“We’re hoping it jogs somebody’s memory,” Lalley said.

She hopes someone will remember seeing the same tackle box years ago in a friend or relative’s home, and she might get the break in the case she needs to solve it.

Harriel said it’s important to her family for this case to be solved. She really wants closure for her family.

“Unfortunately, (Grandpa) was the one who suffered the consequences of somebody else’s actions, and we all live it, every day,” she said. “It’s an unsolved crime. It’s raw. It hurts. It’s difficult to discuss, so we don’t really talk about it.”

The 36th anniversary of the bombing came and went on May 13.

“It’s not a celebration,” Doran said. “It’s really a sad memory.”

She still feels that same unsettling feeling she had the day the bomb exploded, a feeling that will stay in Kimball until this deadly Minnesota mystery is finally solved.

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A $100,000 reward is offered for helping solve this case. Call 1-877-876-2455 with information. You can also contact Postal Inspector Virginia Lalley at 651-293-3237 or Postal Inspector Kate Nichols at 651-293-3220.