Jarno Sebastian Elg was born in 1975 in Finland. Details about his early life are limited, but by his early twenties, he had developed an interest in Satanism and black metal music. He became known for his involvement in the Finnish black metal scene and was associated with individuals who shared similar beliefs.

On November 20, 1998, Elg, along with his 17-year-old girlfriend Terhi Johanna Tervashonka, 20-year-old Mika Kristian Riska, a 16-year-old boy, and a 23-year-old male victim, spent the evening drinking alcohol in Järvenpää, Finland. The group later moved to Elg's apartment in Hyvinkää.

At the apartment, Elg punched the victim, rendering him unconscious. The group then tied him up using duct tape, covering his entire head. While listening to "The Cainian Chronicle" by the Norwegian black metal band Ancient, Elg and Tervashonka proceeded to torture the victim with scissors. The victim eventually died of suffocation due to the duct tape covering his face.

Following the murder, Elg and Tervashonka engaged in acts of cannibalism and necrophilia, including genital mutilation and disembowelment. The victim's head was severed and desecrated before the body was dismembered and disposed of in separate waste containers.

The investigation began when a leg was discovered at a landfill on November 24, 1998. Further searches led to the discovery of additional body parts, allowing authorities to identify the victim through DNA testing. Elg and his accomplices were arrested on December 8, 1998.

In August 1999, Elg was sentenced to life in prison. Tervashonka received a sentence of eight years and six months, while Riska was sentenced to two years and eight months. The 16-year-old boy's charges were dropped, as the court found he had been coerced into participating.

Elg was released on parole in February 2016 after serving 17 years in prison.