On Thursday, 27-year-old Phelim McNally, from Toomebridge changed his plea to guilty, admitting the murder of 18-year-old Lauren O'Neill and the attempted murder of the mother of his two children, Brenda, in a dramatic turn of events.
It came after a jury was sworn in at Londonderry Crown Court on Wednesday to hear the murder case following the double shooting at a south Derry home in William Court on 19 May last year.
In an almost inaudible whisper McNally, from Station Road, in Toome, pleaded guilty before a packed Belfast Crown Court, where his case had been listed at the last minute for mention.
Following the day's surprising turn of events Lauren's father paid an emotional tribute to his late daughter.
Laurence O'Neill told UTV she was the life and soul of their family.
He described her as an all-rounder, adding that she was creative, artistic and full of spirit.
He said: "She was an angel to us when she was living and now she is an angel."
Every time we see butterflies, we think of Lauren, she loved them.
In court, following his guilty pleas, Mr Justice Treacy told McNally the only sentence the court could pass was one of life imprisonment, but that later this month he would "deal with the question of the appropriate tariff", setting out how long he must serve of the life term.
Earlier defence QC James Gallagher had applied to the court for McNally to be rearraigned on both charges to which he had initially pleaded "not guilty" before the jury of six men and six women empanelled to hear the murder trial which was to have started in Coleraine on Monday and expected to last two weeks.
Prosecution QC Frank O'Donoghue then informed Mr Justice Treacy that before McNally's change of plea, counsel in the case had carefully considered the background to the case and the aggravating and mitigating features to it.
Mr O'Donoghue said the prosecution accepted that McNally had only formed the intention to kill after "seeing text messages on Brenda O'Neill's phone, or a short time thereafter".
He also told Mr Justice Treacy that those sets of agreed facts would be typed and handed into court later.
When the jury was sworn, they had been told that at the time of the double shooting Brenda O'Neill was McNally's former partner and Lauren was her younger sister.
They also heard that the three principal witnesses in the case would be Brenda herself and her parents, Laurence and Bernadette.
With the change of plea, they will no longer have to give evidence, neither will McNally's family who were also expected to testify along with paramedics, police and forensic officers, and members of the public.
An earlier court hearing heard that at the time of the horrific shooting McNally's two young children then aged three years, and ten months, were present in the house, before he opened fire.
The court also heard that young Lauren, who had just turned 18, was killed making the ultimate sacrifice, trying to protect her big sister, who managed, despite being seriously wounded herself, to make it to a neighbour's home to raise the alarm over the attack.
Brenda O'Neill, who had to undergo emergency surgery, was to spend over three weeks in hospital and so missed Lauren's funeral, which was attended by, among others, deputy First Minister Martin McGuinness, Mid Ulster Sinn Féin MLA Francie Brolly, SDLP MLA Patsy McGlone and Magherafelt council chairman Ian Milne.
The sisters were both past pupils of St Mary's College in Clady, near Portglenone, and had worked in McNally's Inn and Restaurant on the main Belfast to Derry Road, three miles from Bellaghy.
On Thursday Brenda, surrounded by family and friends left Court 13 at Belfast's Laganside Courtroom, not wanting to comment on proceedings nor on McNally's change of heart.
Phelim McNally (right) who has pleaded guilty to the murder of Lauren O'Neill and the attempted murder of his former partner Brenda O'Neill (pictured left).