Stefán began working for the Icelandic Police in Sauðárkrókur in 1997 and worked there until 1998 when he began working for the Reykjavík police. He began studying at the State Police Academy in 1998 and after graduating, Stefán began working for the Reykjavík police. In 2001, he began working in the National Police Commissioner's Special Unit and worked there until 2007. He began working in the National Police Commissioner's Analysis Department from 2007 to 2008 when he began working as a senior police officer in Sauðárkrókur. Stefán worked alongside his police work at the Ministry of Foreign Affairs and went to Afghanistan as a peacekeeper from 2006 to 2007. Stefán has three children, two daughters and one son.[3]
Stefán was elected to the municipal council of Skagafjörður in 2010 as the leader of the Progressive Party's list. After the 2010 municipal elections, he was elected chairman of the municipality's regional council.[4]
In the spring of 2014, Stefán was appointed chairman of the government's Northwest Committee, which was intended to discuss ways to strengthen the economy and society in Northwest Iceland. The committee submitted proposals. Since December 2014 he was involved in moving the headquarters of RARIK to Sauðárkrókur, as well as some of the activities of the Icelandic Coast Guard, mainly the Guard's ship operations.
