Detectives on Thursday arrested a serving police officer suspected of being the gunman who shot Nairobi lawyer Mathew Kyalo Mbobu dead in September 2025.

Investigators are calling it a major breakthrough.

Mbobu, a former chairman of the Political Parties Disputes Tribunal, was ambushed on September 9, 2025, at around 5:30 pm.

Someone had been following him as he drove home to Bogani in Karen.

Witnesses said the attackers were on a motorcycle and fled after the shooting. He had earlier acted as legal counsel to Prof David Ndetei in court proceedings.

The turning point came from a different investigation.

Prof Ndetei’s wife, Dr Victoria Mutiso, was shot dead in a vehicle in Upper Hill, Nairobi, on July 29, 2026.

Sources say that after suspects in her killing were arrested, some of them allegedly gave police information connecting them to the Mbobu murder.

Dr Mutiso, a former director of the African Institute of Mental and Brain Health, was reportedly embroiled in a land dispute over L.R. Number 1504/13, which is before the Machakos court.

The DCI has flagged the dispute as a possible motive.

Investigators also say she had reported earlier threats to her life.

On July 7, she told police that two armed men on a motorcycle had confronted her near Junction Mall on Ngong Road.

She escaped and reported the incident at Kilimani Police Station.

Ballistic examination

Director of Criminal Investigations Mohamed Amin said detectives had recovered the Ceska pistol that was issued to the arrested officer at the time of the shooting.

Ballistic tests confirmed it was the weapon used to kill Mbobu, which he described as a significant forensic breakthrough.

Amin added that another police officer, who remains at large, allegedly coordinated the operation together with Rose Mbithe.

Mbithe is already in custody over Dr Mutiso’s murder.

The arrested officer is being processed ahead of arraignment. Detectives are questioning him on whether others were involved, and the DCI says other leads are being pursued to establish the motive, planning and execution of the crime.

An armoury gap

Insiders say the case frustrated investigators because the officer allegedly used his service weapon and returned it to the armoury.

That gun was reportedly among those never ballistically tested, as regulations require. The revelation has revived calls for all police firearms to be tested.

The DPP has approved murder charges against Kimutai Maritim, bringing the number of suspects set to be charged over Dr Mutiso’s killing to five.

The others are Rose Mbithe, her daughter Angela Mulwa, her son Chris Mulwa, and Police Constable Elijah Kibelion Kimoi.

All five are due before the High Court on September 29, 2026, for plea-taking, on the directive of Justice Alexander Muteti.

Maritim was arrested on August 22 at Pangani Police Station, allegedly while trying to bring bread and milk to detainees.

Prosecutors have told the court he was allegedly linked to planning the killing and could help trace suspects still at large.

Three other suspects return to court on October 1.