An inspector in the Administration Police and two other people were shot dead in Kahawa West, Nairobi, on Tuesday night.
Kiambu County Police Commander James Mugera said the gunmen also stole the officer's official Ceska pistol, serial number B022698, loaded with unknown rounds of ammunition.
Inspector Michael Ziki, 45, who was the head of the Kiwanja AP post was driving in his car accompanied by John Irungu Kahindu, 43, along Polytechnic Road when they were shot.
The officer was shot twice in the neck from the right side while Mr Kahindu was shot in the chest and face.
As the gunmen were escaping, they shot Mr Eric Munene, 30, a boda boda operator, in his back. He was rushed to Kenyatta University hospital but was pronounced dead on arrival.
Though some eyewitnesses said the attackers were armed with AK-47 rifles, police officers who rushed to the scene collected only 17 rounds of ammunition of 9mm calibre, which were taken for ballistic examination.
SEVEN OFFICERS KILLED
The AK-47 rifles, police say, only use ammunition of 7.62mm calibre.
In the last seven months, several police officers have been shot dead while other have been seriously injured.
On July 1 last year, AP Chief Inspector Achilles Kiwanuka was shot dead and his firearm stolen along Kangundo Road.
On September 3, two National Intelligence Service (NIS) officers were shot and seriously injured before their guns were stolen.
On October 18, Anti-Terror Police Unit (ATPU) Constable Benson Karugu of Kisumu unit was shot in the left side of the chest and in the right thigh in Dandora.
Police records also indicate that on October 29, Police Constable John Mwenda Meme was shot dead in Kasarani.
The local OCPD Robinson Mboloi said the officer was responding to a distress call together with his colleague when he was shot dead.
His colleague was, however, not injured in the 3.18 am attack, about a kilometre from the police station.