A 19-year-old boy under arrest for allegedly murdering a 31-year-old beautician in Hokkaido has told police he just wanted to kill someone, according to investigative sources.

The teenager, a company employee whose name is being withheld because he is a minor, also told the police he does not know if his act was a dream or reality, the sources alleged on Tuesday.

The boy is suspected of stabbing Erika Konno to death with a knife in her first-floor apartment, below the room where he lived, in a two-story building in the Tokachi area. Konno died between Sunday evening and Monday morning.

A knife was found in his unit on the second floor of the building, the sources said.

The police do not think the two had any contact before her death.

Konno was found dead, bleeding from her neck and chest, after a fire was reported in her apartment at around 9:30 a.m. on Monday. The blaze did not spread to any other units in the building.

The boy allegedly said he entered Konno's apartment through an unlocked entrance. He also told investigators he returned to his room and slept after killing her, and then went back to her apartment to set the fire, sources said.