Helge Arnold Fossmo was born on July 27, 1971, in the village of Björneborg, located near Kristinehamn in Värmland County, Sweden. His parents were Norwegian but did not practice a strong religious faith during his childhood. When he was about ten years old, he joined a scouting organization connected to the Mission Covenant Church in his village. By the age of twelve, Fossmo became a "born again" Christian, indicating a significant change in his beliefs.

Fossmo attended high school in Kristinehamn. During this time, he started volunteering at a local Christian youth café. At seventeen, he met Heléne Johansson, who would become his future wife. In 1989, he decided to join the Pentecostal church in Kristinehamn, where Johansson was also a member. After graduating from high school, Fossmo enrolled in Karlstad University to study to become a science teacher. However, he eventually dropped out of the program.

For a while, he worked as a teacher at his old school in Björneborg. In the spring of 1993, he became involved with a small group called Jaspis, which was inspired by a movement known as Livets Ord, part of the Word of Faith movement. After a few months with Jaspis, Fossmo returned to the Pentecostal church, where he took a position as a youth pastor. In May 1995, he organized a "March for Jesus," a public celebration of faith.

Fossmo first met Åsa Waldau in August 1993, when a pastor invited her to Kristinehamn. In 1994, Fossmo's connection to Waldau deepened when his son Samuel became an adherent of her teachings. Helge and Heléne Fossmo relocated to Knutby in August 1997, bringing their two children along. A third child was born while they lived in Knutby.

In Knutby, Fossmo and Waldau initiated a monthly training school that attracted young Christians from various parts of Sweden. This program continued to run three times a year. Additionally, Fossmo started a missionary foundation called Aid for Nations, which initially focused on Estonia before later organizing Bible schools in countries like India and Hong Kong.

The Fossmo family lived next to Åsa Waldau, and Fossmo spent significant time reading the Bible with her. They came to view the metaphorical concept of the "Bride of Christ" as a personal figure. This led to a special ceremony on March 29, 1999, during which Waldau was betrothed to Jesus and took on a new name, Tirsa. Helge Fossmo claimed that as part of his role, he mediated Jesus to her, a statement that Waldau later denied.

On December 18, 1999, Helge Fossmo found his wife, Heléne, dead in their bathtub. An investigation revealed she had a hole in her skull and a high level of a drug called dextropropoxyphene in her blood. Despite these findings, her death was ruled an accident.

A few months later, Helge married Alexandra, who was the youngest sister of his late wife, Tirsa. In June 2001, Helge became ill, and Sara Svensson, a caregiver, moved into his bedroom to help him. Sara eventually divorced her husband, but when it came to Helge, she found herself in a complicated situation. Helge's actions led to Sara being shunned from their church community. During this time, he began an affair with Anette Linde, who was his neighbor's wife.

In the autumn of 2003, Sara started receiving anonymous text messages that she believed were prophetic. With Helge's encouragement, these messages led her to plan the murder of Alexandra. On November 8, 2003, Sara attacked Alexandra with a hammer. Alexandra fought back and managed to call for help, leading to Sara's dismissal from the community. Helge and Alexandra then traveled to a Bible school in Hong Kong, but Helge continued to communicate secretly with Sara.

The text messages returned, and Helge instructed Sara to buy a handgun. On January 10, 2004, Sara followed through with the plan. Alexandra was shot in the head while she was in bed, and Daniel Linde, who was also shot during the incident, managed to call for emergency services and survived.

In the trial that followed, the district court sentenced Helge Fossmo to life in prison for soliciting the murder of Alexandra and the attempted murder of Daniel. However, he was acquitted of the murder of Heléne. Helge appealed the verdicts, but the original sentence was upheld by higher courts. He tried to appeal to the European Court of Human Rights, but his case was not accepted.

In August 2006, Helge admitted guilt in a TV interview and expressed a desire to cooperate with the police. His new lawyer sought to reopen the case, but the police decided against it.

In 2007, while in prison, Helge got remarried. In 2009, he published an article expressing shame for his actions within the church community. Over time, his sentence was reviewed, and in 2014, the Örebro District Court adjusted his life sentence to a fixed 24-year sentence. However, this decision was reversed in 2015, maintaining the original penalty requirements. In late 2019, a new fixed sentence of 26 years was established, and he was released in early 2022.