(NewsNation) — A former member of the Hells Angels Motorcycle Club is accused of arranging to have four people illegally cremated at a California funeral home, according to prosecutors.

Merl Hefferman, 54, entered a guilty plea to obstructing justice in December. Federal prosecutors say Hefferman, an ex-leader of a Hells Angels group in California, helped arrange the cremation of Joel Silva, who once served as the president of the Sonoma chapter of Hells Angels.

Prosecutors reported Silva was shot in the back of the head in 2014, and other Hells Angels members were convicted of killing him.

Prosecutors also allege three other members of the motorcycle group who disappeared — Robbie Huff, Juan Guevara, and Arthur Carasis — were also cremated at the funeral home that was often referred to by the gang as the “pizza oven.” Their bodies have not been found.

According to the Law & Crime Network, the crematory manager at the Fresno funeral home testified that Hefferman was “fascinated with the crematory” and asked for keys to the facility so he could make “something disappear.”

The network reports Hefferman allegedly called the manager the day after Silva died and told him he “better be” at the crematory and that the manager says he was threatened with a gun to load Silva’s body into the incinerator. The crematory manager claims there were three other similar cremations.

Hefferman, 54, is set to be sentenced Thursday. He faces one obstruction charge linked to Silva’s cremation and currently does not face other charges.

Prosecutors are aiming for a seven-year prison sentence, while Hefferman’s attorney is asking for roughly 2 1/2 years in prison.