A UK court has heard how a 15-year-old girl told her brother: "Tell mom I love her," before he murdered her in a fit of rage.

Amanda Selby, from Manchester, had been on holiday with her brother Matthew and father Anthony in a caravan in North Wales. Upon their return to their caravan, the siblings reportedly began arguing and Amanda hit her brother - who is autistic - with a plug, causing a "trivial" injury to his lip, The Independent reported.

Matthew, 20, then lunged at his sister, who fell and became wedged between two beds in the small caravan. Anthony had attempted to intervene, however, he couldn't get to Matthew, who was sitting on top of his sister. He allegedly didn't get up off his sister until she had stopped breathing.

The prosecutor told the court that Anthony had made an "emotional" and "upsetting" call to emergency services. Matthew was reportedly arrested when police arrived at the scene.

According to the outlet, Amanda's cause of death was listed as asphyxiation, having sustained a neck injury from her brother. The court heard how she told him: "Tell mom I love her," as she lay dying underneath him.

[[imagecaption|| Amanda was killed by her brother in a fit of rage at a caravan park in North Wales. Credit: Tommy (Louth) / Alamy]]

Matthew was described by lawyers as having autism spectrum disorder with intermittent explosive disorder, which causes "aggressive outbursts," as well as a depressive disorder.

Per ITV News, Matthew pleaded guilty to manslaughter by diminished responsibility and was eventually handed an extended sentence of 10 years - made up of a five-year custodial term and five years on extended license.

Ahead of the sentencing, Judge Rowlands said the situation was: "An extremely unusual and sad case which presents the court this morning with a difficult task."

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Gordon Cole KC, acting on behalf of Matthew, stated that he had spoken to his mother before the hearing, saying: "This is horrific in the sense that she has, to all intents and purposes, lost two children, but she is very much aware of the issues and difficulties this defendant has and is here to support him."

It was also reported that Matthew had been first diagnosed with autism four years ago at the age of 16 and that his parents had suggested that authorities had not been much help since. He had also been previously convicted of two offenses of battery in 2015, once against his now-deceased sister and another against his mother.

Amanda's family called her a "loving daughter and granddaughter" in a tribute after her death. "She was caring, thoughtful, liked to help others, and very much loved. She will be very sadly missed," they said.

Featured image credit: Hugh Threlfall / Alamy

Court hears girl, 15,'s final words before being killed by brother in 'rage': 'Tell mom I love her'