(Newser) – It's a pretty shocking allegation: that a Missouri couple in their seventies killed their spouses, along with two children, decades ago. But that's exactly what prosecutors allege.

They say Alice Uden, 74, killed her then 25-year-old husband, Ronald Holtz, sometime between Christmas Eve 1974 and Feb. 5, 1975; five years later, they say Gerald Uden, 71, shot wife Virgina, 32, and his two adopted sons, on a bird-hunting outing and hid the bodies.

The crimes both occurred in Wyoming, but much remains murky—motive, whether the Udens knew about each other's alleged crime, and when the two got together.

What is clear are some of the details, which have eluded some 11 agencies that have spent 33 years digging into the crimes, reports KY3.

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A late-August search of a Laramie County mine shaft uncovered the remains of Holtz, whose skull contained a .22-caliber bullet; former wife Alice was actually interviewed in 2005 about the death, but didn't even disclose the fact that she had been married to Holtz. But police say Alice did confess to an unnamed witness, allegedly saying she killed her husband as he slept and moved his body to the shaft in a barrel.

Gerald reportedly confessed on Friday to his crime.

The couple are in jail in Christian County, and will be extradited to Wyoming.

A neighbor tells the AP the two lived on about 60 acres near the Mark Twain National Forest for at least 15 years, with "several of their adult children." (Cold cases like this one, this one, and this one have been making headlines in the last two weeks.)

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