Oliver Tree, the California-born singer-songwriter known for tracks like “Life Goes On,” “When I’m Down” and “Miss You,” died in a helicopter crash in Rio de Janeiro, according to CNN Brazil.

Two helicopters collided over Rio de Janeiro on Sunday morning and crashed in the city’s western zone, killing all six people aboard, firefighters said.

Born Oliver Tree Nickell, the Santa Cruz, Ca., native built a career out of turning absurdity into an art form, blending alternative rock, pop, electronic music and comedy into a singular persona that...