Four gangsters were on Saturday night shot dead in Dandora Phase 2 by Flying Squad officers and a pistol and four rounds of ammunition recovered from them.
Flying squad chief Musa Yego said the four were shot when they fired at police officers.
He said the revolver pistol belonged to the police officer who was shot dead in a Neo Kenya bus on the night of April 27 on Thika Road, near Garden City mall.
Corporal Martin Korir of Ruaraka police station was on the bus on his way home when the vehicle was carjacked by thugs.
He was shot by the thugs and robbed of his Jericho pistol which was loaded with ten rounds of ammunition.
Two other officers from the RECCE Squad survived the attack. Two passengers were also injured during the incident.
Earlier on Saturday, police arrested the Neo Kenya bus driver. The driver was among four suspects who were arrested and questioned on April 30.
The officers who survived the attack on the fateful night said they did not see the official driver being removed from his seat during the entire ordeal.
This raised suspicion that he may have been working in collusion with the thugs.