A “heroic” rail staff member who intervened in a mass stabbing to save the lives of high-speed train passengers suffered life-threatening injuries, police said on Sunday, as a suspect remains in custody.

The member of LNER staff was recorded on CCTV attempting to stop the attacker as the train travelled between Peterborough and Huntingdon in Cambridgeshire, British Transport Police said.

A 32-year-old British national from Peterborough is being questioned after BTP declared a major incident on the 6.25pm service from Peterborough to King’s Cross in central London.

Witnesses described a “terrifying” 14 minutes after the train left Peterborough, with bloodied stabbing victims running through carriages.

The incident on Saturday night led to 11 people being treated in hospital after an unscheduled stop at platform 2 at Huntingdon station.

The suspect, brandishing a large knife, was recorded by a bystander being shot with a Taser as he confronted police on the platform. He reportedly shouted: “Kill me, kill me.”

A 35-year-old Briton who was initially arrested was later released after officers established he was not involved. Five people have since been discharged from hospital.

The BTP deputy chief constable, Stuart Cundy, said: “This was a horrific attack that has had a wide impact. My thoughts and those of everyone in British Transport Police are with those injured and their families – especially the brave member of rail staff whose family are being supported by specialist officers.

“Having viewed the CCTV from the train, the actions of the member of rail staff were nothing short of heroic and undoubtedly saved people’s lives.”

Police said there was nothing to suggest it was a terrorist incident and have asked the public to come forward with any more information.

Both the RMT and TSSA unions were swift to praise rail staff and call for more action. The RMT’s general secretary, Eddie Dempsey, said he would be “seeking urgent meetings with government, rail employers and police to ensure that we have the strongest possible support, resources and robust procedures in place”.

The TSSA’s general secretary, Maryam Eslamdoust, urged LNER and the government “to act swiftly to review security, to support the affected workers, and to ensure nothing like this happens again”.

The driver who stopped the train at Huntingdon was said to be “very shaken” but “good”, and has been commended by an Aslef union officer who said he had done “exactly the right thing”. Named as Andrew Johnson, he is reported to be a Royal Navy and Iraq war veteran.

Last night Johnson, who is from Peterborough, told ITV News: “I was only doing my job.”

Johnson diverted the Peterborough to King’s Cross train to Huntingdon as soon as he was alerted to the attack. This allowed him to stop the train at the platform, instead of passing through Huntingdon and trying to stop further along the track, losing valuable time, the broadcaster reported.

Johnson instead praised his injured colleague, saying: “It was my colleague who is in hospital who was the brave one.”

Nigel Roebuck, an Aslef officer who leads on negotiations with LNER, said: “[The driver] didn’t stop the train in the middle of two stations where it’s obviously difficult for the emergency services to reach, but he carried on going until he got to Huntingdon, where the response was pretty much already there.”

The LNER train left Doncaster in South Yorkshire at 6.25pm. About an hour later, witnesses described scenes of panic on the train as bloodied passengers began to run through carriages warning others of the attack.

Olly Foster said he was in coach H listening to Audible on his phone when a man ran past warning passengers of a man “stabbing everyone, everything”.

“At first I thought: ‘Is it a joke, it’s Halloween, are they pranking?’ But you could see in their faces that this was serious,” he said.

The home secretary, Shabana Mahmood, is expected to make a statement about the attack in the House of Commons on Monday afternoon.

The shadow home secretary, Chris Philp, called for “tough and radical action” in the wake of the incident, including measures such as ensuring more knife crime offenders were jailed, increasing the use of stop and search, and rolling out live facial recognition technology in town centres and train stations.

He wrote in the Daily Telegraph: “We cannot stop every knife crime. But we can – and must – do so much more to get knife crime under control. It is the least we can do for its many victims.”

Police said they received the first distress calls at 7.39pm and the train was forced to make an unscheduled stop in Huntingdon at 7.50pm.

Viorel Turturica, 42, a taxi driver who captured footage of a suspect’s arrest by five officers, told the Daily Mail that, shortly before, he was shouting “kill me, kill me, kill me” to the officers.

Turturica said: “I had arrived at the station pickup point at 7:41pm and was waiting for a passenger. As soon as I see the passenger a few minutes later, I then see everybody running out of the station.

“Then, 10 seconds later, a man dressed in black holding a huge kitchen knife in his hand runs past my car, at 7.47pm. The police arrive seconds later and I could hear him shouting: ‘Kill me, kill me, kill me’ to them.

“They then Taser him and as soon as he is down they say to him: ‘Drop your weapon.’ That’s when I started recording.”

The incident was initially declared “Plato”, the national codeword used by police and emergency services when responding to a “marauding terror attack”, but the declaration was later rescinded.

One of those injured in the incident was a Nottingham Forest season-ticket holder who suffered serious injuries in the process of protecting a young girl during the attack, reports have claimed.

The police released the ethnicity and nationality of the suspect, who is black, following disinformation online which claimed that the incident was a terror attack by Asian Islamists.

It led a former senior figure in Scotland Yard to tell the Guardian that forces were being compelled to disclose the ethnicity of suspects in response to far-right speculation.

Dal Babu, a former chief superintendent in the UK’s biggest force, said: “You will not find pressure on social media to name the ethnicity of suspects when black players are being racially abused on social media.”

LNER, which operates east coast mainline services in the UK, said it expected normal service to resume on Monday, with passengers advised to check their journey online for the latest information.

Anyone with information they believe could help police is asked to contact BTP by texting 61016 quoting reference 663 of 01/11/25.

• Additional reporting: Harry Taylor and Vikram Dodd