Two police officers have been arrested over a shooting incident at Soko Ng'ombe market within Garissa Township.
Via Twitter on Sunday, the national Police directed the Director Internal Affairs Unit Mohammed Amin AIG to immediately carry out investigations into the incident.
NPS also asked the DCI to carry out forensic analysis on the firearms used by the officers.
"The investigations with input from @IPOA_KE and @ODPP_KE shall be able to establish whether the officers were justified to use their firearms or not," NPS said.
The two men were killed and a woman wounded after police fired in the air to disperse a crowd protesting the arrest of a murder suspect.
It started when plainclothes CID officers arrested the suspect who had been on the run for a week, a police officer said, seeking anonymity.
As police were leading the suspect to their vehicle, a crowd gathered, demanding the man be released.
The Independent Police Oversight Authority has opened a probe into the shooting of two Garissa residents.
In a statement on Saturday evening, IPOA said ones they are done with the investigations they will make recommendations.
"I appeal to area residents to maintain calm and report all claims against police officers using the toll free number 1559," Chairlady Anne Makori said.