The suspect in a horrific stalking murder case told police that he killed his female colleague because he blamed her for a potential nine-year prison sentence he was facing for stalking her.

According to the Jungbu Police Station in Seoul on Wednesday, 31-year-old Jeon Joo-hwan likely decided to commit the murder on August 18, the day the sentence was requested by prosecutors.

Jeon had joined Seoul Metro at the same time as the female victim, who worked at Sindang Station on Line Two, but he was suspended after being indicted on charges of stalking and illegally filming her.

He accessed the Seoul Metro intranet four times over the last seven weeks to find the victim's home address and visited the location four times. The address on file was outdated.

After failing to find the victim after visiting a fifth time on September 14, he decided to go to Sindang Station. He allegedly stabbed her to death in the subway station's women's bathroom, one day before he was to be sentenced for stalking the victim.

Police say the crime was likely premeditated, citing the degree of preparations, including bringing a shower cap and gloves from his home in a calculated attempt to prevent leaving evidence at the scene. He also admitted to purchasing the weapon, a knife, because he felt his life was over.