By Sophie Tanno and Catherine Nicholls

(CNN) — Britain was shocked by a mass stabbing attack on a train Saturday evening that targeted passengers as they traveled through central England on their way to London, in an incident Prime Minister Keir Starmer has described as “deeply concerning.”

Nine people were left with life-threatening injuries, one of whom was still fighting for his life in hospital on Sunday evening, after what the British Transport Police (BTP) declared a “major incident.”

Though two suspected attackers were initially detained within minutes of police receiving their first emergency call, BTP said on Sunday evening that only one person is now being treated as a suspect.

A 32-year-old British man remains in police custody after being arrested on suspicion of attempted murder, the authority said, adding that a 35-year-old British national of Caribbean descent has been released with no further action.

Police are working to determine a motive but previously said that there is no evidence to suggest the attack is terror-related.

Here’s what we know about the stabbing attack.

What happened?

The high-speed London North Eastern Railway (LNER) train departed from the northern city of Doncaster at 6.25 p.m. local time on Saturday evening, bound for London.

The train had just left Peterborough station in Cambridgeshire when the attack took place.

Passenger Wren Chambers told the BBC she initially “heard some screaming and shouting” coming from a carriage or two down, before a man ran down the train with a “very clear wound,” bleeding heavily from his arm.

After seeing more people running past, Chambers grabbed her bag and coat. “I got up and moved forward down the train after them, trying to get (as) far down the train as they can.”

People fled through the carriages seeking safety, with some attempting to barricade themselves in the train’s toilets, said other witnesses who saw train seats soaked in blood.

Police received their first emergency call at approximately 7.42 p.m. local time and immediately deployed armed officers. Within eight minutes of the first call, the two initial suspects were arrested after the train made an unplanned stop at Huntingdon station.

Armed police officers were seen running down the platform at the station, evacuating passengers while looking to neutralize any ongoing threat, British news agency PA Media reported.

One eyewitness, who gave his name as Gavin, described seeing one of the men who was initially suspected of being an attacker getting struck down by a police Taser. “Essentially, as they got closer to him, started shouting, like, ‘get down get down’… I think it was a Taser that got him down in the end,” he told Sky News.

The train remained at Huntingdon station Sunday morning, with medical equipment and other debris seen strewn on the platform.

Who are the victims?

A total of 11 victims received treatment in hospital. Ten people were taken to the hospital by ambulance, nine of whom were in life-threatening condition, while another person later self-presented that evening.

As of Sunday evening, one person remains in hospital in life-threatening condition, BTP said. The man, an LNER staff member who was on the train, had “tried to stop the attacker,” it added.

“Detectives have reviewed the CCTV from the train and it is clear his actions were nothing short of heroic and undoubtedly saved many people’s lives,” the statement continued.

Little other information has been given at this stage about the victims, including their ages.

Eyewitnesses have reported seeing people with stab wounds and heavy bleeding.

Who is behind the attack?

Though two people were arrested on Saturday evening on suspicion of attempted murder, police said Sunday evening that one of the men was released from custody after they confirmed that he was not involved.

The man still held by authorities is a 32-year-old, Black British national from Peterborough, where he boarded the train shortly before the attack. He is now being treated as the only suspect in the stabbing.

“Our investigation is moving at pace and we are confident we are not looking for anyone else in connection to the incident,” BTP’s Deputy Chief Constable Stuart Cundy said in Sunday evening’s statement.

“As would be expected, specialist detectives are looking into the background of the suspect we have in custody and the events that led up to the attack,” he added.

Earlier Sunday, police said that there is no indication the attack was terror-related.

“At this stage, there is nothing to suggest that this is a terrorist incident,” British Transport Police Superintendent John Loveless told reporters. “At this stage, it would not be appropriate to speculate on the cause of this incident.”

British defense secretary John Healey described the incident as an “isolated attack” in a Sky News interview.

BTP had initially declared “Plato” – the national codeword when responding to a “marauding terrorist attack” – before rescinding it later.

How common are such attacks in the UK?

The UK rarely sees mass casualty events and homicide rates are low compared to other Western nations.

Gun crime is particularly low, with the country recording 5,103 offenses involving firearms over this past year, according to government statistics.

In comparison, knife crime has risen overall since 2011. Some 51,527 knife crime offenses were recorded by forces in England and Wales in the previous 12 months up until June 2025, according to data from the Office of National Statistics (ONS). Of those, 15,689 were recorded in London.

British politicians and other key figures expressed their shock at Saturday’s attack and offered their condolences to victims.

“My thoughts are with all those affected, and my thanks go to the emergency services for their response. Anyone in the area should follow the advice of the police,” Starmer wrote on X.

Home Secretary Shabana Mahmood said she was “deeply saddened to hear about the stabbings,” and that her “thoughts go out to all those affected.”

In a statement released by Buckingham Palace, King Charles said, “My wife and I were truly appalled and shocked to hear of the dreadful knife attack that took place on board a train in Cambridgeshire last night.”

“Our deepest sympathy and thoughts are with all those affected, and their loved ones,” he added.

“We are particularly grateful to the emergency services for their response to this awful incident.”

The East Coast Main Line – on which the train was traveling – is one of the UK’s busiest and most important railway routes. It connects major cities, running from London King’s Cross to Edinburgh Waverly in Scotland.

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