GREENSBURG — A 49-year-old man who lived with his mother and sister was arrested on charges he fatally shot them, plus an aunt who lived nearby, a year to the day after the women's bodies were found in the small-town glass shop he owned.

Kevin Lee Murphy's mother, Doris Murphy, 69, and sister, Kris Murphy, 43, disapproved of his relationship with a married woman, police said in an affidavit filed with the charges Friday. Murphy's aunt, Edith Teitge, lived across the street and might have been shot simply because she happened by when Murphy was killing the others, police said.

"That's a possibility we are exploring," state police Major Robert Lizik said.

But police and Westmoreland County District Attorney John Peck were not willing to discuss precisely how other evidence spelled out in the affidavit fit together. That included revelations Murphy used his business computer to search for material on incest that focused on "moms," and information about "how to make poison" and "antifreeze how to kill."

Murphy was also trying to acquire nearly $316,000 from the estates of his mother and sister, the affidavit said.

"As far as a motive there were personal interests on the part of Mr. Murphy, but we're not going to get into that right now," Lizik said.

"Suffice it to say, investigators thought that was relevant in terms of understanding completely what this case was about," Peck said, referring to the incest searches, "and what would prompt a person or cause a person to kill his mother and sister and aunt."

The affidavit more clearly links Murphy's secret relationship with a married woman to the killings.

Murphy had been dating a married woman with three children for about two years and planned to move in with them. He told police his mother and sister "did not morally approve of it since she was married."