Ava White, 12, suffered “catastrophic injuries” during an attack in the centre of Liverpool on Thursday night – which is said to be have been seen by children

A youth worker says dozens of “traumatised” children witnessed the alleged murder of a schoolgirl at a Christmas lights switch on.

Ava White, 12, suffered “catastrophic injuries” during an attack in the centre of Liverpool on Thursday night, police say.

The youngster collapsed at the scene – prompting members of the public to desperately try and give her first aid.

Paramedics arrived at around 8:40pm and Ava was taken to hospital, but she sadly died a short time later.

Four teenage boys – one aged 13, two aged 14 and one aged 15, all from Toxteth – have been arrested on suspicion of murder.

It is believed that Ava was attacked on Church Street just after a festive event had taken place, reports the Liverpool Echo.

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Merseyside Police say the area was “very busy” and are urging witnesses to come forward.

Alan Walsh, a knife crime campaigner and boxing gym owner, said he has been flooded with calls from youngsters in the aftermath.

He said: “They were just walking past, some of them were just 13, and they are just traumatised.

I have taken about 12 calls since last night.

“I am just numb. I feel terrible for her family, but also it’s the underlying trauma going on behind it as well.

“You just can’t comprehend it.”

Mr Walsh, posting on Twitter shared anonymised screengrabs from a young person asking to talk.

He said: “The ripple effect of this will be felt for a life time. I took my first text message at 12.09am this morning asking for help.

“Please any young person who has witnessed this horrific incident and needs support please get in touch.

“We will get you councillors and psychologist help.”

One women, posting on Facebook, claimed her son saw Ava lying on the floor “covered in blood”, surrounded by a group of girls.

She said: “They were all crying. He rang an ambulance and another lady came over to help.

“He was so shaken up when he rang me.

“He said it was such a horrible experience to come across this happening to someone so young.”

It also emerged on Friday that Ava was a Year 8 pupil at Notre Dame Catholic College in Everton.

Paying tribute, headteacher Peter Duffy said: “Ava was a much loved, valued and unique member of the Notre Dame family.

“She was an incredibly popular girl with a fantastic group of friends.

“Our deepest thoughts and prayers go out to Ava’s family and friends and all those affected by this utterly tragic event.

“My staff are working with students to provide all the support they need at this traumatic time.”

Ava previously attended The Trinity Catholic Primary School.

Her cause of death has yet to be determined, put police reported previously that officers had been called to reports of a stabbing.

Naming Ava on Friday, assistant chief constable Jon Roy, said: “Our thoughts and condolences go out to Ava’s family, who are being supported specialist Family Liaison officers.

“Their world has been torn apart and no parent should ever have to face that knock on the door from police officers to say that their child has died.

“We believe that Ava and her friends had been involved in a verbal argument which culminated in Ava being assaulted causing catastrophic injuries.

“And we understand that the offenders were then seen to run up School Lane across Hanover Street and on to Fleet Street.

“We have arrested four males aged, one aged 13 years, two aged 14 years and one aged 15 from Toxteth, on suspicion of murder and they are currently being interviewed at police stations on Merseyside.

“Liverpool City Centre was very busy at the time of the incident as the lights on the Christmas tree on Church Street had been officially switched on a short while earlier and we would appeal to anyone who was on Church Street who saw the incident, or may even have captured it on their mobile phone, to come forward.”

Anyone with information is asked to contact Merseyside Police.