In Palmer on Thursday, at about 03:00 an officer told Karen and Jay Priest their son Justin, 29, had been killed.
The devastated couple drove to Justin Priest's girlfriend's home to inform her, when he greeted them at the door.
In fact, another man with the same name but different birthday was killed. The Juneau police apologised for the error.
After hearing the horrible news, the Priests telephoned far-away relatives, then drove to Anchorage to tell their other son in person, they told Alaska Dispatch News.
Then, the grieving family set out to inform Justin's girlfriend of five years.
At her home at about 05:30, Justin Priest said he heard a knock on the door as he was getting ready to walk his dog. Still bleary-eyed from sleep, he was surprised to see his family. All erupted with joy, praising Jesus and embracing one another in tears.
"It opens and right here is Justin. I don't even see it but Jay is sobbing. It doesn't compute to me. Then I see him," Mrs Priest told the Associated Press news agency. "You want it to be true, but you go, 'Am I hallucinating?' Justin didn't know what was going on."
The Juneau police have apologised for the anguish, however momentary.
Justin Priest told the Alaska Dispatch that the family's relief and joy is tempered by the awareness another family lost a son.
Police in a small Alaska town mistakenly told a couple their son had been killed in a car crash, leading to an extraordinary reunion hours later.