Span of crimes
When he was 15-years old, Axlar-Björn began to help in the farm of a rich neighbor named Ormur in exchange for room and board. Ormur died some years later from natural causes and left his estates to his son, Guðmundur. Guðmundur had become friends with Axlar-Björn during his employment, and gifted him a farm called Öxl in the Stadarsveit region of Snæfellsnes. Axlar-Björn took residence there with his wife, Þórdís Ólafsdóttir.
Many legends have been written about Björn and his malice, however these were recorded 250-300 years after the time of the execution. His story is interwoven with legends and full of folkloric motifs. The accounts differ on the motives, modus, number of victims, and events that led to the arrest of Axlar-Björn. Two numbers of victims, nine and eighteen, are the most common claims. The victims were travellers and farmhands that came to Öxl looking for work; some versions say that he hacked them with the axe and others that he drowned them. Local suspicions about Axlar-Björn grew as people disappeared in the area while his horses and other possessions increased, but he was safe because of the protection given to him by Guðmundur.
Arrest and execution
Axlar-Björn was arrested and confessed to nine murders, but authorities found more bodies when they searched his farm. Asked about them, Axlar-Björn claimed that he had found the remains buried in his land and decided to rebury them in another place without notifying authorities or bringing them to a cemetery. The authorities did not believe this explanation. A þing sentenced Axlar-Björn to die by hanging followed by breaking on the wheel. After his death, his body was dismembered and each piece put on a stake. Þórdís, who was pregnant at the time, was forced to watch the execution.
Þórdís was accused of assisting her husband in the murders and even of committing some of the murders herself. She was also sentenced to death, but the execution was not carried out. The son she was carrying, Sveinn "Skotti" Björnsson, grew up to be a vagrant and a criminal, and was hanged for rape in 1648. After Sveinn's own son, Gísli "Hrokur" Sveinnsson, also became a criminal and was executed.
Úlfar Þormóðsson wrote about him in a historical novel, Þrjár sólir svartar (Reykjavík: Höfundur. 1988). Magnús Þór Jónsson included him in his book Björn og Sveinn: eða Makleg málagjöld (Reykjavík: Mál og menning. 1994). And in 2012, the Icelandic theatre group Vesturport set up the play Axlar-Björn which is based on the legends about Björn and his wife.   
- "Axlar-Björn, The only Icelandic serial killer, terrorized travellers on Snæfellsnes peninsula". icelandmag.is. Retrieved November 1, 2019.
- "Oxl, Axlar-Bjorn serial killers of Iceland". nat.is. Retrieved November 1, 2019.
- "Axlar-Björn: The Only Serial Killer of Iceland". medievalists.net. Retrieved November 1, 2019.
- "Þrjár sólir svartar (Three Black Suns)". bokmenntaborgin.is. Retrieved November 1, 2019.
- "Björn og Sveinn: eða Makleg málagjöld". bokmenntaborgin.is. Retrieved November 1, 2019.
- "Axlar-Björn". vesturport. Retrieved November 1, 2019.
- Alda Sigmundsdottir (2019) Icelandic Folk Legends: Tales of apparitions, outlaws and things unseen (Little Books Publishing) ISBN 978-1970125054