MANHATTAN, Kan. (AP) — A Kansas woman who pleaded guilty to killing her 88-year-old mother has been sentenced to 15 years in prison.

Riley County police found June Smith suffering severe stab wounds last Aug. 31 at the Manhattan home she shared with her daughter, 45-year-old Diane Washam.

Washam pleaded guilty in May to second-degree murder. KMAN radio reports she tearfully apologized to her family in court Monday and said she doesn’t understand what happened at time of the killing.

Washam has been diagnosed with paranoid schizophrenia and had not been taking her medication when she stabbed her mother.

District Judge Paul Miller said he believed the 15-year sentence was appropriate under the circumstances. He ordered corrections officials to do everything necessary to keep Washam on her medications and minimize her psychological problems.