July 17 (UPI) -- A Chinese man who avenged the death of his mother was executed Wednesday by order of the Supreme People's Court in Shaanxi Province.
Zhang Koukou killed a family of three as payback for the slaying of his mother more than two decades ago, China's People's Daily reported Wednesday.
Zhang murdered two brothers, and their father, all with the surname Wang, as retribution, according to ABC News.
The death penalty came from the Supreme People's Court. The Intermediate People's Court in Hanzhong City, Shaanxi Province, carried out the execution.
Zhang may have sought revenge after his mother died due to serious injuries, following a quarrel with then-17-year-old Wang Zhengjun in 1996.
Wang was tried as a minor in a Chinese court at the time, and he was sentenced to seven years in prison and ordered to pay about $1,400 in fines.
Zhang "held a longtime grudge" toward Wang and his mental health suffered as a result of his mother's murder, according to People's Daily.
The defendant launched his attack on Wang and his family during the Lunar New Year holiday in 2018. The Wangs had returned to their hometown, and Zhang stabbed the three men to death.
On Wednesday the Supreme People's Court condemned Zhang for taking matters of justice into his own hands.
"The case of the homicide against Zhang's mother has already received legal judgment," the court said. "But Zhang held a grudge for more than 20 years and acted out in vengeance."
The court also said the methods Zhang used were "evil and cruel."
Judges also said Zhang cannot be lightly punished despite his confession to the crime, and that verdicts from his first two trials were "accurate and correct."
According to Amnesty International, China is believed to execute more people annually than any other country, but Beijing does not release numbers.