The suspect in a murder of a young woman in Seoul's upmarket Gangnam district was indicted Sunday, in a case that triggered a public outcry over fears of violent misogyny in South Korea.
Hundreds of mourners attended a candlelight vigil after the 23-year-old victim was stabbed to death by a stranger at a public bathroom in May.
Police have said the murder suspect, a 34-year-old man identified only by his surname Kim who remains in custody, had told them he carried out the attack because he felt "belittled by women".
Prosecutors said Sunday they believed a key trigger behind his murder of a random female victim happened two days before the killing, when the suspect said a cigarette butt tossed by a passing woman had landed on his shoe, Yonhap news agency reported.
The suspect told prosecutors women had caused him a lot of stress, according to Yonhap.
Kim was diagnosed with acute schizophrenia in 2009 and had been repeatedly admitted to hospital. However, he had stopped taking medication in January when he discharged himself.
Seoul Central District Prosecutors alleged Sunday the suspect murdered the woman because he suffered from an untreated mental illness, Yonhap reported.
Prosecutors added their investigation showed Kim was mentally unstable at the time of the murder and should have been in hospital.
But they said it was "difficult" to categorise the murder as a hate crime against women.
"The defendant does seem to have hostility against women, but there was no evidence of him holding indiscriminate prejudice against women," an unnamed prosecutor was quoted by Yonhap as saying.
However, prosecutors said Kim had showed no signs of remorse or guilt.
South Korea generally has a low violent crime rate, but cases of sexual assault have increased in recent years and women's groups argue that entrenched gender discrimination -- rooted in a strong Confucian tradition -- is a prime cause.
A subway station exit near the scene of the stabbing was turned into a mini shrine by thousands of mostly young South Koreans leaving piles of flowers and covering its outer walls with messages written on post-it notes.
The murder and public reaction received wide media coverage, with the mass circulation JoongAng Daily running an editorial entitled "Women at Risk".
In 2013, President Park Geun-Hye directed the police to focus on combating four "social evils" -- the first two being sexual violence and domestic violence.