Gamekeeper Aaron Wilkinson, 24, was found not guilty of murdering 52-year-old Judith Garnett by shooting her in the chest and head.
Wilkinson, who was also diagnosed with a form of Asperger’s Syndrome, told Bradford Crown Court he was not in control of his actions when he shot Mrs Garnett.
He admitted manslaughter earlier on the grounds of diminished responsibility and will be sentenced for that offence at a later date.
The court heard that Wilkinson, of Alma Street, Woodlesford, Leeds, joined the Territorial Army at 19 and went on a six-month tour of duty of Afghanistan in 2009.
While in Afghanistan, he suffered a minor shrapnel wound during an intense two-day battle with the Taliban and later witnessed three Afghan soldiers die in front of him when they triggered an improvised explosive device.
Wilkinson was diagnosed with post-traumatic stress reaction by an Army doctor and has also been found to suffer from Asperger’s Syndrome, or a similar condition, since his return.
He was later assessed by psychiatrists who diagnosed him with the more serious post-traumatic stress disorder (PTSD).
Following his return from Afghanistan, Wilkinson moved into Mrs Garnett’s attic room as a lodger after an argument with his mother in which she had told him she was no longer his mother.
He had worked for Mrs Garnett on her game farm for around 10 years and described her as being like a “second mother” to him.
During this time, Wilkinson applied to join the regular Army but his application was turned down.
He found it hard to adapt to civilian life and motivate himself and his relationship with Mrs Garnett began to deteriorate.
On the day of the shooting, January 24 last year, Mrs Garnett returned home and shouted at him for not letting her dogs out, calling him “thick” and a “cruel bastard”.
Wilkinson said he shot Mrs Garnett three times after she threw his gun up through the hatch into his attic bedroom and told him to “pack his bags”.
The first shot hit her in the chest, the second grazed the side of her face and the third was fired from close range into her head.
Wilkinson said he could not explain why he shot Mrs Garnett and said it was as though he was in a “trance”.
“It sort of just went black and white and hazy at times. It was like I just turned into a mad man,” he said.
“I felt like somebody I’m not.”
Wilkinson said he realised immediately afterwards that he had “done a terrible wrong” and called the police.
Psychiatrists told the court that Wilkinson’s mental conditions meant Mrs Garnett’s order to move out was a “catastrophic” rejection to him after those already received from his mother and the Army.
The court heard that the combination of Asperger’s Syndrome and PTSD left him unlikely to be able to exercise self-control when he felt himself under threat by Mrs Garnett.
This resulted in an “unpredictable, inexplicable, uncontrolled and out-of-character explosive act of violence”.
The jury took around three hours to reach the not-guilty verdict after the two-week trial.