Sean Hackett has been found not guilty of the murder of his father but guilty of manslaughter on the grounds of diminished responsibility.
The former captain of the Tyrone minor football team was accused of murdering his father Aloysius (Wishie) Hackett on 4 January 2013 at their family home in Co Tyrone.
His mother Eilis wept as she sat behind him in the packed public gallery of Dungannon Crown Court.
The 19-year-old had always admitted the unlawful killing of his father, whom he shot twice in the head in the driveway of their Aghindarrah Road family home in Augher.
It took the jury of six women and six men just over two-and-a-half hours to reach a verdict.
Initially, there was some confusion over the not guilty murder verdict and trial judge Mr Justice Stephens asked the jury to retire.
Within moments, he called them back to ask if "all of you" had reached a verdict in relation to the alternative charge of manslaughter and diminished responsibility.
The foreperson said they had reached a guilty verdict on the charge.
Afterwards, Mr Justice Stephens remanded the teenager back into custody until further reports on him are obtained and he is sentenced next month.
The jury accepted the defence's case that Hackett was a mentally disturbed teenager on the possible verge of schizophrenia when he killed his father.
During the trial the jury heard that Hackett, armed with a Czech hunting rifle he had borrowed from a friend, lay in wait for his father, a former chairman of St Macartan's GAA club, to return home from a meeting.
As he got out of his car his youngest son shot him in the back of the head.
He screamed "no", but as he fell to the ground his son had already re-loaded the rifle, and fired again.
Hackett went and felt his father's hand, which was cold, so he said a prayer over him.
The court heard that when first questioned he told police "something was wrong at the house'', possibly a burglary, but later admitted: "I did it ... I shot him."
Later in a prepared statement, he reported: "I was involved in an incident with reference to the death of my daddy whom I love very much ... I have been suffering from depression and was seeking medical attention at the time. That's all I have to say at this time.''
His mother had told the court her son was someone she was "very proud of ... a great boy", but from that day to this she has never asked him why he shot his father.
All she had asked, the court heard, was if her husband had seen him; he had replied "no".
Mrs Hackett said father and son were "almost like brothers'', and that: "We were the perfect family. Sean loved his Dad and vice- versa. Wishie loved him.''
The court had also heard from Tyrone GAA manager Mickey Harte, who described the teenager as a very quiet, “unassuming, lovely young gentleman ... very warm and very caring".
Mr Harte said he had his "eye on him" as a future senior county player and that Hackett, both as a club and county footballer, had a "lot to look forward to".
The jury also heard conflicting evidence from two leading consultants, one a psychologist, called by the defence, the other a psychiatrist, engaged by the prosecution.
While both agreed Hackett had been acting rationally, and logically, and had displayed episodes of self-control, they disagreed about his state of mind at the time of the shooting.
Psychiatrist Dr Fred Browne said Hackett was suffering from "an adjustment disorder" brought on by the break-up with his girlfriend, but that could in no way excuse or explain his homicidal tendencies and the feeling of power, excitement and control he got from thoughts of killing a parent.
The jury accepted the findings of forensic clinical psychologist Dr Philip Pollock, who said Hackett was suffering from a recognised mental condition.
Dr Pollock said he had found while Hackett knew his plans to kill either of his parents was both highly illegal and morally wrong, he was nevertheless driven to commit the slaughter as a solution to his unhappiness and teenage problems.