One individual aged 32 is now the sole suspect after multiple people were attacked with a knife on a train, authorities have stated.
A rail employee remains in a life-threatening state following the attack on a train from Doncaster to London, which stopped in Huntingdon, shortly before 8 PM on Saturday.
A individual aged 35, who was detained at the scene, has been freed with no further action after it was reported "in good faith" that he had been involved in the incident. Police subsequently confirmed this was incorrect.
11 individuals were treated in hospital after the stabbing. On Sunday evening, authorities stated five casualties had been discharged.
The force also confirmed the rail staff member in life-threatening state had attempted to stop the attacker.
"Having viewed the CCTV from the service, the actions of the member of rail staff were nothing short of heroic and undoubtedly saved people's lives," a representative said.
The individual, who is from the city, boarded the London North Eastern Railway train at the local station, the force said.
"Our inquiry is progressing quickly and we are confident we are not searching for any other individuals in relation to the event," stated a police official.
The police said a blade had been recovered by police at the scene.
A senior executive thanked first responders "for their swift and professional response" and said the company and employees were "deeply shocked and saddened" by the event.
"Our thoughts and wishes are with all those impacted, particularly our colleague who continues to be in a life-threatening condition, and their family," he commented.
'People Were Getting Crushed'
A passenger was on the service with a friend when she witnessed a person attacked by a man carrying what appeared to be a big blade.
"It seemed he had a mission to attack anyone he encountered directly in front of him," she said.
"I saw blood all over - people were screaming, 'he's got a blade.'"
Ms Ostalski reported she witnessed someone being stabbed "several seats" from her, adding: "I could have been the next target. People were getting trampled on."
"The train was a very crowded train, so people were just attempting to escape from the attacker, and individuals were tripping, and people were standing on them. The situation was terrible."
After the conductor managed to open a exit at the station, passengers began to flee.
"I doubt I'll be able to travel on a train again," the passenger added.
The driver of the train has been named as the individual.
When the emergency was activated, the driver reportedly notified the control room to get the train rerouted from the main line to the slow track, which has a stop at Huntingdon.
The driver's decisions are believed to be why first responders were able to access the service so rapidly.
His fast response likely prevented the train from stopping in the middle of nowhere or needing to go to the next station, which would have required 10 to 15 minutes.
A trade union officer stated the driver is "very shaken" but "good", and commended him for doing "precisely the correct action".
"The driver did all he was instructed to do, at the right time and in the right way," said a union official.
"The driver demonstrated real courage, genuine commitment, and real resolve in the toughest of situations."
A further observer, an individual, said: "I must note there were certainly numerous brave individuals on that occasion, many caring people who just wanted to assist those around them - individuals providing coverings, heat packs."
The witness said he observed one hurt individual who had been cut in the head. He was told the person was "attempting to protect a child from being harmed".
"The individual took that injury to the face out of protection for her - that's true real altruism, without a doubt."
"I witnessed multiple individuals smeared in blood, and seeing how serious their wounds were, I understood this is an event really, really severe."
