A woman in her 40s was sentenced to 15 years in prison for killing her 11-month-old nephew by throwing him from a 24th floor apartment.

The Daegu District Court’s western branch on Thursday found the woman guilty of murdering the baby and ordered the 15-year sentence as well as five years of probation.

Delivering the verdict, the court said “the victim died in pain, unable to express himself and the mother will live in pain with emotional scars.”

She was convicted of killing the baby on May 8, which was Parent’s Day in South Korea, at an apartment where her younger brother and his wife live in Dalseo-gu, Daegu.

The investigation revealed that the woman had held the baby after asking the baby’s mother if she could. When the mother briefly left the room, the defendant locked the door and threw the baby off the balcony.

Authorities said the defendant had a history of mental illness, including antisocial personality disorder and depression, for which she had been hospitalized. After her release from the hospital, she developed delusions that her family would kill the infant, leading her to commit the crime.

At the scene of the crime, she had reportedly told the mother that “I euthanized him,” and “If he goes to the hospital, they will kill him painfully.”

The prosecution had earlier sought a 20-year sentence, a 10-year electronic ankle monitor and five years of probation, arguing the crime was premeditated.