SALT LAKE CITY (AP) – A Utah businessman who worked a two-year sting operation for federal officials investigating looting of American Indian relics across the Southwest has died of a self-inflicted gunshot after a brief standoff with police.

It appears to be the third suicide connected to the case.

Ted Dan Gardiner, an antiquities dealer and former grocery store CEO, shot himself Monday in his bedroom in a Salt Lake City suburb, police said.

Gardiner, 52, was the government’s lone operator in a sweeping federal investigation that led to felony charges against 26 people in Utah, Colorado and New Mexico on charges of trafficking in artifacts.

Gardiner’s father and his son told The Associated Press on Tuesday they didn’t know why he killed himself. Federal authorities declined comment.

The trouble began Saturday, when Gardiner’s roommates called police to say he was suicidal. Officers confiscated a handgun from Gardiner and he was transported to a hospital for a mental health evaluation.

On Monday evening, roommates called authorities again after gunshots rang out in Gardner’s bedroom. An officer confronted Gardiner, who refused to drop his gun. The officer felt threatened enough to fire a round at Gardiner, but the shot didn’t hit him, Police Lt. Don Hutson said.

Gardiner was later found dead in his bedroom of a single gunshot.

Two defendants – a Santa Fe, New Mexico, salesman and a prominent Blanding, Utah, physician, James Redd – committed suicide after their arrests in June.

Gardiner offered in 2006 to help federal authorities set up what turned into a long-running sting operation in the black-market trade in prehistoric relics.

Gardiner provided prosecutors with hundreds of hours of video showing suspects admitting they took artifacts from federal and tribal lands, according to court documents.

The case broke open in June when about 150 federal agents descended on the Four Corners region. In the small town of Blanding, Utah, agents raided homes of 16 people. Most were handcuffed and shackled as agents confiscated stone pipes, woven sandals, spear and arrow heads, seed jars and decorated pottery.

The arrests prompted outcry from southern Utah residents – many claiming federal officials were heavy-handed. One man served a year in federal prison for threatening to track Gardiner down and beat him with a baseball bat.

Two of the 26 defendants – Redd’s wife and daughter – pleaded guilty last year. The rest pleaded not guilty.

Copyright 2010 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

AP-CS-03-02-10 2201EST