A private guard who shot and killed an unarmed herder in Gilgil has been arrested and the gun he used to execute the heinous act recovered.

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The guard from Marula farm was arrested on Sunday and detained at the Gilgil Police Station hours after the killing.

The arrest came as members of the Maasai community demonstrated along the busy Nairobi-Nakuru highway over the killing of 27-year-old Mandela Ole Kitaita.

The protests led to a heavy traffic in Gilgil as the Maasai morans blocked the highway, which was opened after local leaders intervened.

Trouble started on Sunday morning when the herder whose cattle strayed into the ranch was shot and killed on the spot. He was shot from the back.

Gilgil sub-county commissioner Ndambuki Mutheki said the guard is being held at the Gilgil police station as investigations continue.

He called for calm as law enforcers wind up investigations into the criminal act.

"The police have managed to arrest the main suspect in this case and also recovered the shot-gun used in the killing," Mutheki told Radio Jambo.

Gilgil MP Martha Wangari who visited the area told police to ensure justice is delivered.

She expressed concern over the rising conflicts between ranchers and herders in the semi-arid constituency.