Patrick Njenga, 31, was reportedly hit on the head by the group when he tried to stop them from fighting at a bar in the area.
The youths turned against the soldier for asking them to stop their fight.
His death sparked protests on Thursday as family demanded that those involved in the mysterious murder of the officer be punished.
The residents urged the government to close bars in Nyataragi, adding that most of them have turned to be dens for bhang peddling.
"The men are from the same village. We first thought they were playing but the fight turned ugly," Kevin Kimani, a resident, said.
Area deputy county commissioner David Kiprop said the matter was reported at Mutarakwa police post.
"One suspect has been arrested and is helping police with investigations into the incident," Kiprop said.
-The Star