A ‘lovely’ teenage girl was killed in her own bedroom in a terrifying knife attack that left her mother seriously injured.

Lainie Williams, 17, was found fatally wounded at her home in Cefn Fforest, near Blackwood, South Wales, at around 7am on Thursday, while her mother Rhian Stephens, 38, was airlifted to hospital for treatment.

Armed police later arrested an 18-year-old man in nearby Newbridge on suspicion of murder and attempted murder, with detectives confirming they are not looking for anyone else.

The alleged attacker is said to have waited for Rhian’s boyfriend to leave the house for work before letting himself into the house through an open door.

Relatives said the knifeman stabbed the mother before running back into Lainie’s bedroom, where she was sleeping.

College student Lainie, who had been looking forward to her forthcoming 18th birthday, died at the scene, and her mother was being treated in hospital for serious knife wounds.

Lainie’s great-grandmother, Florence Jones, 78, said: ‘Her mother said Lainie put up a fantastic fight against him.

‘I’m in total shock, she was a lovely bubbly girl. She lived with me for the last few years, I can’t believe what’s happened. Things like this don’t happen in our family.’

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Lainie Williams (pictured) was pronounced dead at the scene of the incident on Wheatley Place in the Cefn Fforest area of Blackwood, Gwent

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Lainie’s great-grandmother, Florence Jones, 78, described the schoolgirl as a ‘lovely bubbly girl’. Pictured: College student Lainie, who had been looking forward to her forthcoming 18th birthday

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Rhian Stephens, 38, was airlifted to hospital for treatment following the attack

The alleged attacker was seen outside the house without a shirt on at 5.30am on Thursday.

He waited for Rhian’s boyfriend, Clive Osborne, to leave for work at 7am, then let himself in through an open door and went upstairs to where Lainie was sleeping.

Her grandfather Robert Stephens said: ‘He lunged at Lainie with the knife and her mother heard her screams.

‘Lainie’s brother Carter came out of his room and Rhian told him to get back in and hide under the bed.’

Armed police were called to the family’s three-bedroom former council house in the village of Cefn Fforest, while paramedics arrived in an air ambulance but were unable to save Lainie.

Rhian’s mother Ceri was at her bedside in the hospital tonight while little Carter was being looked after by his father.

Neighbours, who said they woke to the sounds of sirens, helicopters and banging doors, described Lainie as ‘the loveliest person’

Local Michelle Davies said: ‘It is terrible. That poor girl had everything to live for and now she is gone.

‘At least the mother survived but she will never get over what she witnessed.’

Mother-of-two Rhian had lived in the semi-detached house for at least five months.

She was described as a ‘caring person, but who kept herself to herself.’

Another neighbour added: ‘Lainie was the loveliest, kindest person who had a lot of friends. The girls are in bits.’

One local said they were awoken by the sounds of helicopters landing near his home before seeing ‘chaos’ outside.

He said: ‘It’s usually a very quiet area, you don’t expect something like this to happen on your doorstep.’

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Police at the scene on Wheatley Place in the Cefn Fforest area of Blackwood, Gwent,on Thursday morning

Detective Superintendent Philip O’Connell, the senior investigating officer for Gwent Police, confirmed the force is not looking for anyone else in connection with the incident

He said: ‘We understand that reports of this nature can be concerning, and it is likely that residents will see an increased number of officers in the area while we carry out further inquires.

‘If anyone has any information, please speak to our officers or contact us in the usual way.’

Cefn Fforest Councillor Shane Williams said: ‘We are all deeply shocked and saddened by the events that have unfolded, and I understand that the police are not looking for anyone else in connection.

‘But as councillors, we’d like to do our best to reassure everyone, and our thoughts are with the family at this time.

‘We are all hoping for a full recovery for the woman who was hospitalised. Something like this is highly unusual in this area, and I can understand if many residents are now frightened.

‘When a young girl loses her life like that, it’s quite horrendous.’

Independent Councillor Kevin Ethridge added: ‘As the local county councillor for Blackwood, I’d like to send my condolences to the family.’