YouTuber KSI has shared an emotional tribute to US singer-songwriter Oliver Tree, who was killed in a mid-air crash between two helicopters in Brazil, according to local reports.The helicopters collided over Rio de Janeiro on Sunday morning, killing all six people onboard both aircraft.Tree was listed on the passenger manifest of one of the aircraft which crashed into a car dealership in the city’s western zone, igniting a fire that was subsequently extinguished. Police have not yet been able to formally identify the bodies of the victims.Tree, a 32-year-old American artist, collaborated with KSI on the track “Voices” and is widely known for his hit “Miss You.”Six people died in a helicopter crash in Rio de Janeiro, Brazil, Sunday morning (AFP/Getty)Taking to X, KSI expressed his profound grief, writing: "Can’t believe I’m actually having to type this. You’re 32 man. You should still be here. You still had so much life to live. So much music to make. So much content to make. You’re a legend and will always be a legend. Still doesn’t feel real. Genuinely feel sick. I love you bro."Jackass star Steve-O, real name Stephen Glover, paid tribute to the late singer in a post on Instagram.Sharing a photograph of the two together, the US comedian and prankster said: “I was incredibly lucky to become friends with Oliver Tree.“He would check in on me regularly, and let me know he cared about how I was doing. Such a great person, f***, I’m going to miss him…”Enjoy unlimited access to 100 million ad-free songs and podcasts with Amazon MusicSign up now for a 30-day free trial. Terms apply.Try for freeADVERTISEMENT. If you sign up to this service we will earn commission. This revenue helps to fund journalism across The Independent.Enjoy unlimited access to 100 million ad-free songs and podcasts with Amazon MusicSign up now for a 30-day free trial. Terms apply.Try for freeADVERTISEMENT. If you sign up to this service we will earn commission. This revenue helps to fund journalism across The Independent.Tree was only weeks into his ambitious World’s First World Tour, which aimed to see him perform on all seven continents. He had recently played in Buenos Aires, Argentina, on 4 June, and shared a video of himself playing football in a Brazilian neighbourhood just the day before the incident. His tour schedule included more than 70 shows across 30 countries, with upcoming UK dates in Glasgow, Manchester, and London slated for September.In 2024, he received a Brit Award nomination for International Song alongside German producer Robin Schulz for “Miss You,” which peaked at number three in the UK singles chart. Oliver Tree collaborated with KSI (pictured) on the song “Voices” (Getty Images)Beyond his musical career, Tree also held a Guinness World Record, achieved in 2020, for the largest kick scooter, measuring 0.16m tall and 3.13m long, a feat he reportedly undertook to "fulfil a lifelong dream".According to AP, content creator Gaspar Prim Diaz – also known as Gaspi – was also believed to have been in one of the helicopters.Gaspi had more than 2.8 million followers on YouTube and was 23.In a tribute shared on X, Argentine streaming channel Blender said: “Thanks for your art, your magic and your sensibility, every one of us will miss you.”Officials have launched an investigation to determine the cause of the collision.