HUNTINGDON — UK police were Sunday investigating a mass stabbing on a London-bound train that injured several passengers, with a British national the sole suspect in an incident not being treated as a terrorist matter “at this stage”.

Here’s what we know so far

What happened? 

Police were alerted to an emergency on board a train between Doncaster, a town in north-east England, and London’s King’s Cross Station — a typically busy route — at around 7.40pm (1940 GMT) on Saturday night.

The train was stopped at Huntingdon station in Cambridgeshire, where armed officers backed by police cars, a fleet of ambulances and two air ambulances swarmed the station in the eastern England market town.

“Police boarded the train and arrested two people within eight minutes of the first 999 call,” Superintendent John Loveless from the British Transport Police told reporters at a briefing on Sunday.

In an update later Sunday the police said they had released one of the two arrested men “with no further action”.

While 10 people were initially taken to hospital, five were later discharged. One victim, a member of the rail staff who tried to stop the attacker, remained in a life-threatening condition late on Sunday.

The head of the transport union RMT, Eddie Dempsey, commended the train crew, driver and operators “who quickly assisted in diverting the King’s Cross-bound train into Huntingdon station”.

“The actions of the member of rail staff were nothing short of heroic and undoubtedly saved people’s lives,” the police said.