The teenager said he was unsure of how to use the flare which went into the San Jose support killing Kevin Beltran Espada after it stuck him in the face.
The 17-year-old told Globo: "We were celebrating the [Corinthians] goal. I took the flare from my bag, pulled on the cord, didn't quite know how to use it. It took off in the direction of the Bolivian fans."
With his face hidden due to his age, the teenager went on to say, “I feel like I'm the worst person in the world. I don't know what I'll do with my life, I deeply regret what happened.''
Two of 12 fans of the Brazilian club that have been detained in Bolivia have been formally accused of setting off the flare that killed Kevin, with the others being held as accomplices.
After the incident the South American football federation announced that Corinthians’ fans will be banned from attending their matches for the next 60 days - a punishment that the current Copa Libertadores champions have appealed against.