A 15-year-old girl screamed for her mum as she was beaten and robbed on a tram.
The victim was travelling from the north Manchester area into the city centre when she was set upon last month, reported MEN Online.
It is understood she was sat in the final carriage of a double-length tram when she was surrounded by a group of teenage boys and girls and subjected to a vicious and unprovoked attack which left her needing hospital treatment.
One of those allegedly involved filmed the incident on their phone – and reportedly shared the sickening footage on social media, further humiliating the victim.
The video shows a girl repeatedly punching the victim around the head before dragging her to the floor, where she is further kicked and punched.
At one point, the teenager can be heard screaming for help and begging for her mum.
Her iPhone was stolen during the incident.
The victim's older sister wanted to share the video to illustrate the severity of the attack and call for greater security for those travelling on the Metrolink network.
Officers from the Greater Manchester Police anti-robbery unit Operation Valiant launched a swift investigation following the incident on April 19 and have made four arrests.
Two girls aged 14 and one aged 16 were arrested on suspicion of robbery. Another girl, 15, was arrested on suspicion of assault.
All have been bailed pending further inquiries.
The victim's iPhone has also been recovered.
As the investigation continues, police are asking anyone who might have further information to come forward.
"It's just horrendous," the victim's sister said.
"The lads were egging [the girls] on.
"They were putting the video on Snapchat and laughing about it.
"I posted it on Facebook because I wanted show the parents what their children are up to."
It is believed the tram driver was unaware of the incident as it happened in the rear carriage.
The victim got off when the tram stopped in the Piccadilly area and was helped by a passer-by who called the police and an ambulance.
She was taken to hospital, where she was treated for bruised ribs and a dislocated wrist.
"There were other adults on the tram – but nobody did anything, not one person intervened," the victim's sister said.
"You would have thought there would be a natural reaction, just to say 'get off', just speaking out.
"But not one person did anything."
The victim's family says she has been left deeply traumatised by the attack and continues to struggle with her mental health.
"We're just trying to keep her busy and happy as much as we can do," her sister added.
"She's doing better now.
"It was such a vicious attack.
"I think people need to be aware what's going on on the trams."
Greater Manchester Police said in a statement: "Operation Valiant became aware last week of a video in circulation on social media of an incident on a tram going through the City Centre on the 19th of April 2020.
"Over the last week we have arrested two girls aged 14 and one girl aged 16 on suspicion of robbery and a further girl aged 15 on suspicion of assault (attempted grievous bodily harm).
"All four girls have been bailed as the investigation continues.
"Anyone who may have witnessed this incident at the time is asked to call 101 quoting CRI 06A2/0008443/20."
Danny Vaughan, Head of Metrolink at Transport for Greater Manchester, said: "This was a terrible experience for the victim, and nobody should be subjected to attacks on the tram network. We take security on Metrolink very seriously, and anti-social incidents like this are absolutely unacceptable. That’s why we’re working to tackle this type of behaviour in partnership with Greater Manchester Police’s Transport Unit through the TravelSafe Partnership.
"We fully support Greater Manchester Police with this investigation, and I would urge people to call 101 if they have any information, or if they witness any behaviour that causes concern in the future.”