The U.S. Department of Agriculture's wildlife services tried to help hunt down the wolf, but fly-overs in the area produced few results.
Swigert killed the wolf on Friday afternoon when he spotted it near his horse pasture.
An Idaho Department of Fish and Game spokesman said the rancher had the correct hunting tag and didn't break any laws when he shot the wolf.
Fish and Game couldn't verify that the animal Swigert shot was the same wolf that killed his colt.
But the rancher is certain it was the same animal.
"We can be sure that the distinctive track we have been following for five long weeks belonged to this wolf," Swigert wrote. "Justice has been served for the painful death of our horse."
Steve Alder of Idaho For Wildlife wrote before the wolf was shot that Swigert and his wife were worried about reprisals from "radical wolf advocates."
"Elite, highly trained retired special forces officers have been on the ground watching their home almost 24 hours a day," Alder wrote Feb. 27 on the website.
Information from: The Times-News, http://www.magicvalley.com