Police in Kisii are looking for a man who disappeared together with his wife and children from Botibigi village after allegedly spearing to death his neighbour.
A motorcycle operator said he saw the attacker drinking the blood of the victim.
In retaliation, villagers razed two houses belonging to the suspect.
The irate mob also destroyed several avocado trees and a banana plantation belonging to the suspect.
Villagers said the suspect attacked the 38-year-old man when they met on a road on Monday evening.
The victim's wife, Rispah Kwamboka Obara, said her husband had left home and said he was going to collect a Sh1,600 debt from a friend.
"I do not know what happened on the way. We just received news later that my husband had been speared into his heart after he met with his assailant on the road," she said.
Gucha South police boss Moses Kanyi said officers are trailing the suspect, who escaped via Trans Mara and was tracked in Sirare en route to Tanzania.