Sergeant John Kipyegon Kemei, who served in the office of the Deputy President William Ruto, was found with a gunshot wound to the head.
Local media report that he was at work on the day a former Kenyan cabinet minister visited the office accompanied by directors from an American firm to discuss an arms tender.
The former minister, Rashid Echesa, has since been charged with forgery. The US firm Eco Advanced Technologies alleges that Mr Echesa approached them with a fake deal to supply arms to the Kenyan military, and also allege that Mr Echesa swindled them out of $113,727 (£88,204) in consultation fees