The suspect, Erick Kamau (24), allegedly stabbed his mother early on Tuesday morning, killing her on the spot.
His twin brother, Derrick Mwangi, was stabbed in the chest after trying to intervene and save their mother from the attack.
According to Ruiru’s Director of Criminal Investigation (DCI) Director, Justus Ombati, the deceased had recently registered the suspect at a psychiatric institution so that he could get the help he needed.
The injured brother, Mwangi, is being treated at Saint Joseph Hospital while the body of the deceased has been taken to a funeral home at Kenyatta University.
Police are currently pursuing the suspect.