A teenagerhas died after hitting his head off a railway bridge as his friends filmed his 'train surfing' exploits for a Tiktokvideo.

The group of four ‘train surfers’ were riding on the roof of a trainat up to 50 kph in Vienna, Austria, on October 26 when the grisly accident occurred. The grim collision has claimed the life of one teen, who died in hospital three days after the incident with a second, who suffered massive head injuries, still fighting for his life.

Meanwhile, the other two are unharmed, and within hours of the deadly smash, a video of their friends’ gruesome injuries on the train roof had been uploaded to social media. The grisly clip starts showing two urban surfers riding on the roof of the train as it roars through the city's Meidling suburb at speeds of up to 50 kph (31 miles per hour).

The teens can be seen riding on the roof of the urban commuter train (

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The incident happened while the teens were riding on top of a train in Vienna, Austria (

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In the footage, the boys flatten themselves on the roof of the carriage passing under the top of the tunnel with just inches to spare. But as the train comes to a station disaster strikes, when two of the boys have turned their backs to face into the camera and so do not see a low footbridge coming up fast.

One of the group shouts a desperate warning saying: "No, no, no, no!" But they don’t react in time and a split second later there's a sickening crunch as both teens' heads slam into the bridge.

Shockingly the others keep filming and get closer for a gory close up of their two friends as they lay twitching on the carriage roof with blood flowing from massive head injuries clearly close to death. Screams from horrified passengers who had been waiting for the train can be heard coming from the platform as the footage comes to an end.

Schoenbrunn Station, in Vienna, Austria, where the incident happened (

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One 17-year-old was declared brain dead three days later, on October 29, and died when his parents agreed to his life support being terminated, Local media reports on Saturday said. His friend, who is 18, is still fighting for life after he suffered catastrophic head injuries. Meanwhile, their two pals, aged 13 and 16, suffered only minor injuries.

Rail chiefs have warned teens about the high risk of the social media craze for subway surfing. A spokesperson said: "We urgently appeal to them to refrain from such reckless and life-threatening actions.

"No TikTok video, no example of courage or selfie in the world is worth climbing on a subway or tram and risking one's life. If you notice a dangerous situation, please immediately operate the emergency call facilities in the vehicles or on the platform."