Three gunmen and a police officer were killed in an attack on DP William Ruto's Sugoi home on Saturday.
Police sources said the fourth suspect was shot and fatally wounded.
The four gunmen ambushed the home shortly after Ruto left for a rally in Kitale. GSU guards and workers were the only ones at the residence at the time.
It is feared several workers are trapped in the home.
Witnesses said the gunmen are Somali and that they had pretended to be selling sheets.
They said the attackers burned the guard's house after getting into the compound.
A GSU officer guarding the gate was shot and injured and his gun snatched before fighting began.
A corporal in charge of the home's security was killed.
Gunshots could still be heard at the home, where it has been established the attackers gained access to the armoury.
About eight Recce Squad officers entered the home in a bid to contain the situation.
The Recce Squad arrives at DP William Ruto's Sugoi home following a gang attack on July 29, 2017. /MATHEWS NDANYI
Rift Valley regional coordinator Wanyama Musiambo and Uasin Gishu county commissioner Abdi Hassan are among security chiefs at the the scene.
MPs Oscar Sudi (Kapseret), Alfred Keter (Nandi Hills) and several aspirants are among people waiting near the home.
Journalists and members of the public were kept about 400m away.