Lyndon ? A former Missouri city official charged with killing his estranged wife, their two daughters and his wife’s grandmother in Kansas snapped because of his wife’s lesbian affair and was mentally a “shell of a man,” his defense attorney said Monday as his trial got under way.

Prosecutors are seeking the death penalty for James Kraig Kahler, 48, in connection with the four shootings, which occurred the weekend after Thanksgiving 2009 just outside Burlingame, about 20 miles south of Topeka, in the home of Kahler’s estranged wife’s grandmother. His trial in Osage County District Court is expected to last at least two weeks.

Osage County Attorney Brandon Jones described the shootings as premeditated. Prosecutors began their case by presenting evidence putting Kahler at the scene of the killings, including testimony from Kahler’s 12-year-old son, who was in the home when the shootings began but escaped without being physically injured.

“The defendant proceeded to go through the home, targeting each and every one of the females in that home,” Jones said Monday during his opening comments to jurors. “He fled the scene and left them to die.”

Prosecutors did not discuss Kahler’s motives for the shootings. But during his opening statement, Thomas Haney, a Topeka attorney representing Kahler, described him as a loving husband and father who appeared to have a perfect family life for more than two decades before his marriage turned “cancerous” in 2009.

“No one but a person with serious mental illness would do what Mr. Kahler did,” Haney said. “He had a psychotic break and he snapped.”

The victims of the shootings were Kahler’s estranged wife, Karen, 44, her grandmother, Dorothy Wight, 89, and the Kahlers’ two daughters, Emily, 18, and Lauren, 16. Only the oldest daughter was found dead at the home; the others died in a Topeka hospital later.

Loss of job, marriage

The killings came less than three months after Kahler was asked to resign as water director in Columbia, Mo., amid a contentious divorce and facing a domestic assault charge stemming from an altercation with his wife.

The four deaths are covered by a single count of capital murder because Kansas law allows the death penalty for multiple murders arising from a single “scheme or course of conduct.”

As an alternative, the state also has filed four counts of first-degree murder, carrying a sentence of life in prison. Kahler also faces one count of aggravated burglary because, prosecutors contend, he broke into Wight’s home.

Haney said defense attorneys will present evidence showing that a woman from Weatherford, Texas, broke up the Kahlers’ marriage, and that Kahler suffered a mental breakdown. The family lived in Weatherford before Kahler took the Missouri job in 2008.

Haney said Kahler was so mentally ill that he can’t be held responsible for his actions. He said months before the killings, Kahler was even having hallucinations and was prescribed medication, though he didn’t take it.

Son’s testimony

Kahler’s son, Sean, was among the first witnesses to testify. The defendant smiled briefly as the slight boy entered the courtroom and took a seat in the witness chair. The boy held a yellow tennis ball with a smiley face and answered questions solemnly.

The boy said his father did not threaten him, and neither of his parents said anything. The boy, who’d often fished and hunted with his father, testified that he recognized the weapon his father was carrying. He was 10 at the time of the shootings.

“My dad came in and shot my mom,” the boy testified.

During his questions, Haney asked the boy, “After all you’ve been through, do you still love your dad?”

The boy replied, his voice shaking a little, “Not really.”

The state’s list of witnesses includes Sunny Reese, the woman referenced in court documents as having a relationship with Kahler’s wife. Jones said prosecutors’ questions for her would be brief.

There was no answer Monday at a telephone number listed in Weatherford under Reese’s name in an Internet directory, and she did not respond to a message seeking comment left at a business number.

Karen Kahler’s brother, Bill Hetrick, who lives in the Wichita area, also testified briefly. Haney prompted him to recall an email by James Kahler that Hetrick received shortly before the shootings, saying Karen Kahler had recently spent time with Reese, with the Kahler children present.

Hetrick replied by email that he was sorry for what the Kahlers were experiencing but told James Kahler it was time for him to move on. Hetrick also said, based on James Kahler’s email, “The situation has obviously driven you to extremes that are not healthy.”