Investigators say a man who fatally shot a Colorado sheriff's deputy and wounded two others trying to serve an eviction notice used a rifle he legally purchased four years ago.

The Colorado Bureau of Investigation said Friday that Martin Wirth bought the .45-caliber rifle from a private seller in February 2012. Authorities say the 58-year-old killed Cpl. Nate Carrigan and injured two other officers Wednesday at his foreclosed home near Bailey, about 45 miles west of Denver.

The deputies fired back, killing Wirth. He was acquitted of killing a man more than 20 years ago and had recently threatened to shoot police. But authorities say they never expected the eviction to erupt into violence.

Master Patrol Deputy Kolby Martin is hospitalized in fair condition. The other deputy was grazed by a bullet.