An Administration Police officer on Thursday afternoon shot and killed his girlfriend before turning the gun on himself in Isiolo town.
County Commissioner John Ondego said the officer was 47 years old and that he had served for 25 years. He was employed in 1993.
The commissioner said the officer had just had lunch at the AP line, where his lover operated a canteen.
The two reportedly quarrelled before the officer shot the woman who was in her early 40s. He then killed himself.
"This is a regrettable and unexpected incident since the officer had been deployed in the morning for his normal duties," Mr Ondego said.
The commissioner noted that such cases have been reported countrywide and are common among security forces.
He advised them to seek proper dispute resolution mechanisms, including help from their seniors, instead of resorting to murder and death by suicide.
The bodies were taken to the mortuary at Isiolo County Referral Hospital.
At the Kenya School of Government in Mombasa, where he met coastal region commanders in November, Inspector-General Joseph Boinnet said they were worried about the high number of such incidents.
Mr Boinnet’s driver, Anthony Lemayan Lenkisol, died by suicide early in December while on sick leave.
Cases have also been reported of police officers turning their guns on civilians, and the civilians retaliating.
“We want to support officers who require help because of the tremendous stresses that police work exerts on us. Majority of police officers work very well but a few, occasionally, break down,” Mr Boinnet said.
"We have created a department of counselling and are in the process of decentralising the service to regions. With enough resources, we will go further into the counties."
The National Police Service Commission established a Counselling and Rehabilitation Centre in October to address psychosocial or stress-related problems affecting officers