An uncle of the 11-year-old boy killed subway surfing in Brooklyn blames himself and social media for the boy’s tragic death. Victim Cayden Thompson was riding on top of a G train when he struck his head on an overhang at the Fourth Ave./Ninth St. stop in Park Slope, fell to the tracks and was run over by the train about 10:10 a.m. Monday, cops said. “He got into this situation looking up to me,” said Christian Vega, 15, who is Cayden’s uncle but calls the victim his brother because they were both raised together by Christian’s mother. “He thinks if I can do it, he can do it.” “I’m an ex-subway surfer,” Christian explained in an exclusive interview. “I used to do it. He would see videos online, not only mine, but other kids’ videos. He would always think things were a competition.” On Monday morning, Cayden’s grandmother, who is Christian’s mother, walked Cayden from their home in the Whitman Houses to Fort Greene Preparatory Academy, where Cayden just started sixth grade. But the boy soon slipped out of school unnoticed and headed for the subway, according to Christian. “He left school somehow … They should’ve stopped him. And nobody did. That’s how he went on that train,” Christian said, adding that his mother normally keeps a tracker in Cayden’s backpack but it was missing that morning. The city Department of Education is investigating what happened that day. “My heart is broken for the family, friends and loved ones of this young child, taken from us far too soon,” Schools Chancellor David Banks said in a statement to the Daily News. “Subway surfing is a dangerous epidemic in our city, and the risk is never worth it. I implore all our community members to check in on the young people in their lives and remind them to always ride inside. We are providing additional supports to this school in the coming days and weeks.” Police investigate after Cayden Thompson was killed subway surfing at the Fourth Ave.-Ninth St. station in Brooklyn Monday. (Gardiner Anderson for New York Daily News) When Christian noticed his younger brother had taken an interest in the deadly stunt several months ago, he alerted his mother, Cayden’s grandmother. “Me and my mom we were both telling him how dangerous this is,” Christian said. “I told him every day not to follow in my footsteps. It’s dangerous. I would tell him every single day. It’s not good. You’re going to get yourself hurt.” Christian and his mother even tried taking Caylen’s cell phone away to limit his access to YouTube and TikTok videos of subway surfing. “He still had the idea. He would always talk to me about it. Like ‘Yo I’m gonna do this. I’m gonna do that.’ And I would keep on saying ‘No, don’t do that!’,” Christian said. Despite repeatedly trying to dissuade his little brother, Christian said he can’t help but blame himself. “I feel guilty,” he said. “I feel like I’m the one that caused this.” Cayden Thompson (GoFundMe) But Christian said the influence TikTok and YouTube had on his younger brother, who is diagnosed with ADHD, was too powerful to resist and demanded that companies remove content that glorifies the dangerous stunts. “Take everything off the internet. Everything that has to do with #subwaysurfing #urbex take it all down, everything that has to do with that,” he fumed. “They need to make a law that kids under the age of 14 and 13 can not have a cellphone.” An MTA spokeswoman said agency staff continue to flag social media posts glorifying subway surfing. To date, according to the MTA’s data, 10,650 such posts have been removed across various social media platforms. “This is another avoidable heart-wrenching reminder that riding outside trains is not a game, and the subway is not a social media studio,” Demetrius Crichlow, NYC Transit’s interim president, said in a statement Monday. Christian remembered Cayden as an energetic kid who loved playing Fortnite and scootering at the skate park. “He always wanted me to teach him to skateboard. I never got that chance,” he said. “He was very outgoing. He would always connect with people. Every time we would go to the park he would make a new friend. He was a very good kid. He never caused no trouble.” Cayden dreamed of playing professional football or basketball before his life was cut short on the rails. “He was always talking about being an NBA or football star. He was more into football. He plays with me and other friends.” Cayden’s grandmother, who raised the boy as her son, is taking the news hard. “She’s sleeping in his room,” Christian said. “She can’t let go of the fact that it happened.” Cayden is the youngest victim in recent memory to die subway surfing. In March, cops caught a 10-year-old attempting to ride atop an A train in the Rockaways — but were able to remove him from the train and return him to his mother before he could be hurt. Cayden is the fourth victim to die subway surfing this year. All the victims were boys under 16. Christian began subway surfing at age 11, the same age Cayden was when he died. “I’m never gonna do it again. After this never. I won’t even think of going in the tunnels anymore,” Christian said. “All that stuff is dead to me because I lost my little brother. He should still be here doing other things. His whole life was ahead of him.” With Cayla Bamberger, Thomas Tracy, Rocco Parascandola and Evan Simko-Bednarski