A call to a mental health caseworker with a harrowing threat touched off Wednesday night's hours-long standoff in Butler that ended when police shot and killed a man who refused police orders to drop a handgun that he had aimed at them.

Keith George Tack also threatened to blow up his house in a gas or bomb explosion, authorities said.

"He made a suicidal comment to the caseworker that there were bombs in the house and that he had rigged the gas line to blow, said Butler County District Attorney Richard Goldinger.

No such devices or booby traps were found in Tack's downstairs apartment of the two-story duplex at 425 Bredin St.

But the 48-year-old man's desperate remark set off a series of events that would end in his death. Investigators suspect that was the ending Tack wanted.

Three state police officers opened rifle fire about 8:30 p.m. when Tack walked out of his house and pointed a handgun at the officers.

Tack was hit three times, once in the chest and twice in the shoulder, according to an autopsy done Thursday.

The gunshot wound in the chest likely killed him, said Deputy Coroner Larry Barr.

Police said Tack shortly after 5 p.m. had holed himself up with a weapon at his home after threatening to hurt himself.

Butler police said they called for the state police Special Emergency Response Team after going to the home and seeing the man with a gun and hearing several shots inside.

A T.W. Phillips gas crew also was called out, primarily due to Tack's earlier threat to blow up the house using natural gas.

But those workers were unable to shut off the gas due to the fear Tack could shoot them, company spokesman Jay Dawson said.

The gas would not be shut off, he said, until 8:45 p.m., 15 minutes after Tack was fatally shot.

Despite continued negotiations that night, Tack refused to give up and surrender.

Goldinger said police eventually decided to take action and fired tear gas into the house.

"They were always concerned about the threat," Goldinger said, "and wanted to defuse the situation."

Investigators said Tack walked out onto the back porch with a pistol. Police ordered him to drop it. Instead, he raised the gun.

"He would not put the gun down per their command," Goldinger said, "and he aimed it at them."