Oliver Tree, the eccentric singer known for viral hits like “Alien Boy” and “Life Goes On,” has died at the age of 32 following a helicopter crash in Rio de Janeiro.

Officials in Brazil on Monday were inspecting the site of a crash in which six people were killed Sunday, after two helicopters collided midair over a suburb of Rio de Janeiro.

Fernandes de Freitas, a tyre repair worker, said he saw one of the helicopters in flames following the midair collision, and noticed that one of the passengers jumped out of the other aircraft, before...