Two security guards attached to President William Ruto's National Security Advisor Monica Juma were forced to open fire on Saturday night after a lone gunman attacked them along the Mwingi-Garissa highway near Nguni market.
The aides, drawn from the military police, were caught off guard when the gunman, believed to be a foreigner, stopped them on a deserted stretch of the highway.
Dr Juma, a former Defence Cabinet Secretary in the government of former President Uhuru Kenyatta, wasn't in the car.
According to an incident report filed at Nguni police station under case number, the two bodyguards, who were armed with pistols, were travelling from Nairobi to Mwingi East - Dr Juma's rural home.
The officers were ordered out of their vehicle and robbed at gunpoint. As he fled, the assailant fired three shots, prompting the armed officers to open fire, killing him instantly.
The officers searched his bag and found several items including Somali currency, food, a solar panel and 38 bullets packed in a small black bag. His gun, an AK-47, had 23 bullets.
"Also found in his possession were two pairs of open shoes, a small sauce pan, a knife, a solar panel, 15 dry batteries, scissors, a pen and an electric tester," the report said.
Detectives in Kitui are trying to establish the identity of the attacker and how he managed to terrorise motorists for days while hiding in the bush.
Moments earlier, the gunman attacked a St Andrews Academy water tanker in Mwingi, spraying the truck with bullets.
The lorry driver, identified as Patrick Mutie, told police that he saw a man with a gun who signalled him to stop, but instead he sped away.
Suddenly, the driver heard three shots and realised that his right front tyre had been hit, but decided to continue with the flat tyre until he reached Nguni market.
The body of the gunman was taken to Mwingi Level Four Hospital mortuary while investigations continued.