American singer Oliver Tree was among those killed when two helicopters collided in Rio de Janeiro, Brazil, on Sunday. A police source confirmed Tree was on the passenger list of one of the downed aircraft during his global tour. All passengers aboard both helicopters are confirmed dead, totaling six individuals. Formal identification of the victims is currently delayed due to the severity of burns sustained in the crash. Authorities are investigating the cause of the collision. The incident occurred while Tree was performing in Brazil as part of his world tour. Further details are expected as the investigation progresses and identification processes are completed.