A man who desperately sought help as his sister had a seizure on a train was told by a Southestern employee he "did not care" about the issue as it was causing delays.
The rail provider will now investigate the incident, which happened on a service in the county.
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University student Nichelle Kelleher was travelling home on Monday when she suffered an epileptic fit.
Her brother went to find help but upon coming across an employee says he was to he "did not care as he was holding up the service".
After coming round Nichelle confronts the railway enforcement officer who admits he said he "did not care what he was saying as he was delaying the train".
He said: "You're not having a fit now are you?
"If you were having one now I would care for you."
Nichelle filmed the encounter and was told: "You're more than welcome to put this on social media.
"No I did not care for what your brother was saying at that moment in time because he was delaying a carriage train full of people. OK?"
He refused to give his name but did provide a badge number.
The video was shared on the Instagram account of The Black Project, a group which seeks to amplify black voices in Britain.
It said: "The arrogance of this employee honestly made my blood boil. He was smug stood there, you could tell he thought he was better than Nichelle and her brother and he wouldn’t face any consequences for this blatant disregard of human life.
"Also he claims 'if you were having a fit now I would be worried and I would care' but when she was having a fit he didn’t care, and the only thing he [was] worried about was the train being delayed. So he risked her life for a time schedule, and then tried to gaslight her to her face.
"@se_railway what is your response? Is this the type of man you want interacting with your customers? Representing your brand?"
A Southeastern spokesman said: “We’re sorry for any upset to those in the video. We take the wellbeing and safety of our passengers very seriously and are investigating this fully.”