Steen Viktor Christensen was born on October 9, 1964, in Denmark. Details about his early life are limited, but by the early 1990s, he had become involved in serious criminal activities, including multiple bank robberies, hostage-taking, and rape. In 1992, he was convicted in Denmark and sentenced to 12 years in prison for these offenses.​

In the autumn of 1997, Christensen was granted an unguarded prison furlough, a common practice in Denmark aimed at rehabilitating prisoners. However, during this leave, he escaped and fled to Finland, adopting the alias "Kim Anderssen."

On October 22, 1997, while in Helsinki, Finland, Christensen robbed the Palace Hotel. During his escape, he encountered police officers Sergeant Eero Holsti and Senior Constable Antero Palo on Tehtaankatu street. In an attempt to avoid arrest, Christensen shot and killed both officers.​

The double homicide triggered an unprecedented manhunt in Finland. Christensen was eventually apprehended on October 25, 1997, in Hämeenlinna, as he was leaving the Hotel Vaakuna, where he had been staying under his assumed name.

During his trial at the Helsinki District Court, Christensen admitted to the murders and expressed no desire to appeal his sentence. Despite his objections, he was sent for a mental health evaluation at the Niuvanniemi mental hospital. He refused to participate in any psychological assessments, leading to the cancellation of the examination. Nevertheless, the Finnish judicial center of health care (TEO) concluded that Christensen was fully aware of his actions and deemed him a dangerous repeat offender.​

On May 7, 1998, Christensen was sentenced to life imprisonment. He was also ordered to pay nearly 275,000 Finnish marks (approximately €46,300) in compensation to the families of the slain officers, the state treasury, and the hotel watchman. Additionally, he was mandated to provide a monthly support payment of 3,873 Finnish marks (about €651.40) to one underaged child.​

Following his conviction, Christensen was transferred to Herstedvester Prison in Denmark, a facility known for housing some of the country's most dangerous criminals. The Danish Ministry of Justice allocated four million Danish kroner (around €500,000) to enhance the prison's security measures specifically to prevent any escape attempts by Christensen.

While incarcerated, Christensen married a Finnish woman in 2000, who later gave birth to their child. Some sources suggest that his wife is a former cross-country skier named Miia.​