The three men arrested are now in custody and face imminent court appearance as investigations intensify.
The suspects Carlos Owiti, 24, alias Kalonje from Nyalenda; Eric Otieno, 39, alias Dude from Manyatta and Vincent Odhiambo 27, alias Tinga from Nyalenda were picked up by DCI officers in Kisumu County.
They stand accused of taking part in the brazen attack that targeted the senator at Java House inside West End Mall.
Authorities described the operation as a direct response to credible leads that surfaced soon after the incident.
With the trio now behind bars detectives say they have stepped up efforts to track down any remaining accomplices.
The arrests mark an early victory in what appears to be a coordinated probe aimed at restoring calm in the lakeside city.
Sources close to the investigation indicate that forensic work and witness statements played a crucial role in identifying the men so quickly.
The Directorate of Criminal Investigations has publicly praised ordinary citizens for stepping forward with vital information.
In an official statement DCI urged continued public cooperation stressing that every tip helps build a stronger case.
We thank members of the public who volunteered useful information the agency noted adding that further updates will follow as the case progresses.
Political observers view the swift action as a strong signal against rising insecurity targeting public figures.
Senator Osotsi a respected voice from Vihiga commands significant influence in western Kenya.
The attack at a popular mall spot has sparked widespread concern among residents and leaders alike with many calling for full accountability.
As the suspects prepare for their first court date focus now shifts to the broader investigation.
With three men already in custody and more names possibly on the list the message from DCI is clear justice will not wait.
The people of Kisumu and beyond are watching closely to see how many more will be brought before the law in the coming days.