One 32-year-old man is now the only person of interest following multiple people were stabbed on a train, police have confirmed.
A rail staff member remains in a critical state following the incident on a train from Doncaster to London King's Cross, which halted in Huntingdon, shortly before 20:00 GMT on the weekend.
A individual aged 35, who was arrested at the scene, has been released with no further action after it was reported "in good faith" that he had been implicated in the attack. Police later clarified this was incorrect.
Eleven people were treated in hospital after the attack. On Sunday night, police stated 5 casualties had been released.
The force also confirmed the employee in critical state had attempted to halt the assailant.
"After examined the CCTV from the train, the actions of the employee were truly brave and undoubtedly preserved people's safety," a representative said.
The suspect, who is from Peterborough, entered the London North Eastern Railway train at the local station, the authorities said.
"Our inquiry is progressing quickly and we are confident we are not searching for anyone else in relation to the incident," stated a senior officer.
The police confirmed a knife had been recovered by officers at the location.
A senior executive expressed gratitude to first responders "for their swift and professional actions" and said the company and staff were "profoundly stunned and distressed" by the incident.
"Our thoughts and wishes are with everyone impacted, especially our colleague who remains in a critical condition, and their loved ones," he commented.
'People Were Being Crushed'
A passenger was on the train with a companion when she saw a person attacked by a individual holding what appeared to be a large kitchen knife.
"It seemed he had a purpose to stab anyone he saw directly in front of him," she said.
"I saw red everywhere - individuals were yelling, 'he has a knife.'"
Ms Ostalski reported she witnessed someone being stabbed "five or six rows" from her, noting: "I might have been the next target. People were being trampled on."
"The train was a extremely busy service, so passengers were just trying to run away from the assailant, and people were falling, and others were standing on them. The situation was terrible."
After the staff member managed to unlock a door at the stop, people began to escape.
"I don't think I'll be able to sit on a train anymore," the passenger concluded.
The operator of the train has been identified as the individual.
When the emergency was activated, Mr Johnson reportedly contacted the control room to get the service diverted from the main line to the local line, which has a stop at the station.
Mr Johnson's decisions are believed to be why first responders were able to access the train so rapidly.
His quick thinking likely avoided the train from halting in the remote area or needing to go to the next station, which would have required ten to fifteen minutes.
A representative stated the operator is "quite distressed" but "okay", and commended him for doing "exactly the right action".
"The driver did everything he was trained to do, at the appropriate time and in the right manner," said a representative.
"The driver demonstrated true courage, genuine commitment, and real determination in the most difficult of situations."
A further observer, Thomas McLachlan, said: "I must note there were definitely numerous heroes on that day, several kind people who simply wanted to help those around them - people providing coverings, heat packs."
Mr McLachlan said he saw one injured man who had been cut in the head. He heard the person was "attempting to defend a young girl from being harmed".
"He received that wound to the head out of protection for her - that's true genuine selflessness, right there."
"I saw several people smeared in red, and seeing how severe their wounds were, I realised this is an event really, really bad."
