A soldier killed two teenage runners with his "loaded weapon of a hot-hatch car", the mother of one of the victims has said as he was jailed.
He was jailed for six years at Winchester Crown Court on Thursday after Lucy's mother Lisa Pygott accused the "selfish" 24-year-old of robbing Britain of future Olympic medals.
After Casey, 24, was told he should be out of jail on licence in three years, Stacey's emotional mother Helen stood and shouted from the public gallery: "I don't get my daughter back in three years, do I?"
After the hearing, she also broke down in tears screaming: "Three years, three years!"
The court had heard Casey, who was awarded the "most promising soldier" accolade in his platoon, was over the drink drive limit when he hit the teenagers.
The pair were training with their club Aldershot, Farnham and District Athletic Club and had correctly crossed at a set of traffic lights in Aldershot, Hants, when Casey hit them.
The court heard the soldier, based at the Normandy Barracks in Aldershot, could have been travelling up to 52mph in his Ford Focus ST and flung Lucy 30 metres, and Stacey 45 metres.
Casey had been at a leaving do with fellow soldiers and told police he had "three or possibly four" pints as well as a cocktail to himself which included three shots of whisky and three amaretto shots.
The court heard Casey had given a lift to a colleague after leaving the pub in Aldershot who vomited in the car, and was distracted at the time of the collision by this vomit.
Mrs Pygott gave the emotional statement as dozens of family members wept in court during the hearing.
She explained how her daughter was told by her coach she had to potential to run for Team GB in the Olympics.
Mrs Pygott said: "Lucy was extremely beautiful, nearly six feet tall, blonde and blue eyes.
"Not only that but she was extremely talented. Three days before her death she ran the fastest time in a cross country race she loved.
"Her coach said she was the next big thing for Britain in running with Olympic potential. Mr Casey robbed this country of medals, of what level? We don't know.
"She had Oxbridge potential. She should have had the opportunity to go on to do some good in the world.
"She was an absolute joy to our family, she was the glue that gelled us together. Her warmth, energy, dancing and daft sense of humour was all shattered needlessly when Mr Casey killed her and it's utterly unbearable that I'll never see her again.
"Mr Casey selfishly took away all her future hopes of love, marriage and the child she one day hoped to have and in doing so, Mr Casey has robbed us of our future and the grandchildren we will never have.
"The utter devastation that Mr Casey has wreaked has left me desolate to the core. Every occasion is now ruined by the complete futility of her death.
"He severed Lucy from her brother and sister that evening and I wish Mr Casey could hear them cry at night like wounded animals.
"The full impact of her death is unknown but we have to watch them suffer.
The British army trains soldiers to kill and he killed. He killed with his loaded weapon, a hot-hatch car
"There is nothing I can say, do, or anywhere I can go that alleviates the pain. The only thing which would cure it is having Lucy back and that's never going to happen."
She continued: "Mr Casey has broken our precious family and we are lost without Lucy.
"I believe with every decision there's an opposite choice. On that day he had a choice, he chose to put the key in the ignition.
"He chose to turn the key, he chose to accelerate, break the speed limit, drive through a red light and brutally mow them down all while knowing he was drunk.
"The British army trains soldiers to kill and he killed. He killed with his loaded weapon, a hot-hatch car.
"Lucy followed the rules crossing correctly and she should have been safe. Mr Casey didn't follow the rules and killed her.
"He gave her no choice, she stood no chance. She is buried while he is alive and has been living at home and retains his driving licence and passport.
"He still has rights and choices but Lucy does not. Any feelings of guilt Mr Casey feels does not compare to the pain we have to feel everyday.
"Maybe he will become a father one day as he still has choices.
"I would like to say this to him - when you look at your child for the first time, feel the unconditional love and urge to protect them, keep them safe, then you might understand a tiny fraction of how your actions have made us feel."
Prosecutor Kerry Maylin told the court Casey, who spent six months serving in Afghanistan, drank pints of beer and a 'Godfather' cocktail made of three Jack Daniels shots and three Disaronno shots.
She said another young runner, William Smith, was next to the girls and shouted 'run!' when he noticed Casey's speeding car.
Ms Maylin said: "It was apparent the car was not going to stop so he shouted 'run'. He moved in time but unfortunately the girls didn't."
She added: "Another witness was driving behind Mr Casey, he was travelling 30mph when he saw Mr Casey accelerate with maximum acceleration."
Examination showed his breath test measurement would have been 46mcg per alcohol in 100mm of breath. The legal limit is 35.
Casey told police "normally he has a two-pint limit" when driving. He admitted two counts of causing death by dangerous.
James Newton-Price, defending, said read out an apology from Casey. He said: "Mr Casey wishes to say I'm truly sorry to the Burrows and Pygott families. I'm sorry for the loss and suffering I will have forever caused you."
Judge Cutler, also banning him from driving for 10 years, said: "Sadly, both these children had immensely golden futures ahead of them."