"I can't say why; there's no reason," the man told police during an interrogation.
The woman was shot while standing on the platform of the central train station in Umeå on Saturday morning, July 20th and later died in hospital.
"My plan was to shoot at a pole or some sign or a window. But never at a person. It was never my intention to do that," the 21-year-old told police, according to the Aftonbladet newspaper.
During a hearing at the Umeå District Court on Wednesday, the man was charged with murder. While he has admitted to shooting the woman, he doesn't feel the crime should be classified as murder, in part because he can't explain why he shot the victim.
"He really hasn't given any motive whatsoever," said prosecutor Magnus Öhm.
Olle Andersson, head of the major crimes unit with the Umeå police, told reporters what the suspect did prior to the fatal shooting, explaining that the 21-year-old had partied at a restaurant in central Umeå.
He then received a ride home, at which point he hopped in a car and drove off. He then shot at a window in a house before heading to the train station.
"He then saw a woman walking and fired a shot at her. The shot hit the woman in the upper body," said Andersson.
The killing is considered very unusual as the victim and the shooter had never met.
"During the investigation, we couldn't find any connection at all between the man and the woman who was shot," said Andersson.
Nor is there any connection between the shooter, the victim, or the residents of the house whose window was shot.
Two people are expected to testify that the man was at the station at the same time the woman was shot.
The 21-year-old is also facing charges of reckless endangerment (framkallande av fara för annan) stemming from shooting at the house, and aggravated weapons crimes, as he didn't have a licence to own the gun.