Rear Admiral Stig Olof Bergelin (20 September 1905 – 5 October 1983) was a Swedish Navy officer.

This led to a multi-year service in the Nautical Department of the Royal Swedish Naval Materiel Administration, combined with service as a teacher of navigation at the Royal Swedish Naval Academy and - in summer - as navigation officer on the seaplane cruiser HSwMS Gotland, also flag adjutant at the Naval Academy Department.

[5] In all, during his career as a naval officer, he served more than 15 years at sea, except for six months in 1936–1937 in civilian shipping company under temporary employment in Rederi AB Transatlantic [sv].

[4] Under World War II, Bergelin served as a teacher of navigation at the Royal Swedish Naval Staff College from 1941[6] and captain of the destroyer HSwMS Gävle from 1942 to 1944,[5] when he was promoted to lieutenant commander.

At the same time, he was a teacher in navigation at the Royal Swedish Naval Staff College's higher courses and in naval warfare at the Royal Swedish Air Force Staff College.

[5] After the war Bergelin first became executive officer and then captain of the cruiser HSwMS Tre Kronor in 1948.

[7] The position as commander of the 1st Destroyer Division (1. jagardivisionen) in the Coastal Fleet was held by Bergelin from 1950 to 1951.

[10] Bergelin attended the Swedish National Defence College in 1957 and for the next two years, he served as head of Section 2 in the Naval Staff.

In 1959, Bergelin returned to his hometown and to the technical-administrative position as head of the Karlskrona Naval Yard (Karlskrona örlogsvarv), where his authority and organizational skills were, among other things, an asset during the thorough reorganization of the administrative service and the creation of a civilian shipyard.

He was succeeded as head of the South Coast Naval Base by Captain Hans Gottfridsson [sv].

[11] After leaving active duty, he quite logically ended his career as the first chief executive officer of AB Karlskronavarvet [sv] from 1967 to 1969.

About an hour before the crime, the man had agreed with a doctor at Gullberna Mental Hospital that he would be allowed to come there for treatment.