Many fled the scene screaming in terror
Police arrived at Forest Hill station at around lunch time after a “horrific” attack had taken place on a train.
A knifeman chased and threatened bystanders after stabbing a passenger, witnesses said.
Witnesses said there was a huge presence of emergency services at the station, they warned people to avoid the area as the attacker was “ranting on the streets”.
One woman said she arrived at Forest Hill at about 1:30pm when she saw dozens of passengers fleeing the station.
She told the Evening Standard: “Around 30 people were running out of the station screaming. There was a guy there pacing around and shouting ‘I’ll take everyone on’.
“I asked people what had happened and they said he had stabbed someone with a knife. I called the police.”
A spokeswoman from British Transport Police confirmed that officers were called to the scene at 1.18pm.
A statement read: “One person has been arrested on suspicion of GBH following the incident and is currently in police custody.”
“One man was treated by ambulance staff at the scene and is currently en route to hospital.”