A 68-year-old woman from Bokoma village in Boncharia was burnt to death for allegedly using sorcery to kill her 11-year-old grandson.
The boy and his younger brother are said to have stolen some avocados that had fallen from a tree planted within their grandmother's compound two weeks ago.
The granny is said to have sought the services of a witchdoctor who conducted rituals in the compound to 'arrest' the alleged thief.
After the death of the grandson early on Tuesday, angry villagers stormed the home and demanded answers from the elderly woman.
She reportedly confessed to having sought the services of a witchdoctor.
According to the boy's father, his son complained of persistent headache that lasted two weeks.
"For two weeks, I have talked to my mother. She has been silent since then. She alleged that my two sons had stolen avocados from her compound and threatened to kill them," said the tearful father.
He added: "I don't know what to say. Whenever she was drunk, she would threaten to kill anybody who dared touch her property."
The mother of the children said her son complained of severe chest pains.
"My mother-in-law has never given me peace since I married her son in 2006," she said.
The deceased woman's husband ran away from home immediately his wife was killed.
The body stayed at the scene for more than four hours with nobody willing to assist police carry it.
Kisii South OCPD David Mburukwa warned residents against taking the law into their own hands.
On Tuesday morning, more than 50 youths caught the granny off-guard while attending to her farm and set her ablaze.