MARION, UTAH, JAN. 28 -- A burst of gunfire today ended a tense, 12-day standoff between a polygamist clan and police. One officer was killed, and the clan's ringleader, suspected of bombing a Mormon chapel, was seriously injured.

The shooting erupted just after dawn as police who had infiltrated the clan's compound used a dog to try to isolate Addam Swapp and his brother from the log house the two had left moments before, officials said.

In the exchange of gunfire, the dog's handler, Lt. Fred House, 35, was shot fatally in the abdomen and Swapp fell in the snow with bullet wounds in the arm and chest, said John T. Nielsen, state public safety director.

Neilsen said agents in an armored personnel carrier evacuated the wounded and "came under extremely heavy gunfire" from the house.

Moments later, the clan's four other adults -- including Vickie Singer, whose husband died in a shootout at the compound nine years ago -- and nine children filed from the house in two groups with their arms raised above their heads. Officials had maintained they would not storm the house for fear of harming the children, five of whom were placed in foster care today.

The siege began within hours of the bombing Jan. 16 of a Mormon chapel a half-mile from the clan's 2 1/2-acre compound. That night, Swapp told police that the bombing was in revenge for the 1979 police slaying of polygamist patriarch John Singer. Swapp has said he sought an armed confrontation to trigger Singer's resurrection.

Nielsen said the decision to seize Swapp, 27, on federal warrants was made after a family friend delivered to police Wednesday afternoon Swapp's response to a letter from Gov. Norm Bangerter pleading with him to surrender. He said Swapp "declared his ranch and people an independent and free nation" and warned he would use any means to defend it.

Vickie Singer, Swapp's mother-in-law, was taken from the compound to a federal courthouse in Salt Lake City for arraignment on charges related to the Jan. 16 church bombing and today's gunfire. She pleaded not guilty and was ordered held without bail for a hearing Monday.

John Singer was killed nine years ago by police trying to arrest him after an 18-day standoff. Singer, who had defied a court order to send his children to public schools, allegedly drew a gun before he was killed.

Swapp, married to two Singer daughters and father of six of the clan's children, was rushed by ambulance to a Heber City hospital, then was airlifted to the University of Utah Health Sciences Center in Salt Lake City. He was reported in serious but stable condition.

Swapp's brother, Jonathan, 21, was not injured.

Legislators briefed by the governor were told that police had been planning Swapp's capture for several days. Early today, law officers were close to taking Swapp into custody, but could not isolate him from the main house, they said.

Officers tried again to trap Swapp by installing a booby-trapped loudspeaker designed to set off a bright flash when moved, to blind Swapp so police dogs could move in to subdue him, the legislators said.

Instead, they said, Swapp shot at the loudspeaker, apparently tipping it over and triggering a flash less bright than authorities had hoped. The dog-handler, apparently thinking the booby-trap had worked as planned, advanced toward Swapp and was shot.

Ogden Kraut, a longtime family friend who took the governor's letter into the house and brought out Swapp's response, said Swapp and Singer remained firm in their belief that an armed confrontation with police would trigger her dead husband's "resurrection."

"I sort of feel like I failed," Kraut said today, "but I did all I could. There was only two ways it could end. They could either give up, or shooting."