Seven people were killed in an early morning attack at Lokichoggio AIC Secondary School in Turkana on Saturday.
The attackers are suspected to be Toposa bandits from South Sudan.
They killed six students - four boys and two girls - and the watchman and injured 18 others.
The attack is said to have arisen from a conflict between two students.
Form one student Abraham Lojore, who is from South Sudan, has been accused of going to the school with three assailants.
He had been expelled
from the school for indiscipline cases.
Students claimed he threatened to return to the learning institution and exact revenge for the punishment he was given.
A survivor who is also a learner from the neighbouring country termed
Lojore a friend.
"The 27-year old once worked with South Sudan Defence Forces before coming to study in Kenya. I was to be killed so I wouldn't reveal any information about him. I am lucky to be alive."
The attackers killed the watchman before proceeding to the dormitory.
It is said they called students who had been reporting the indiscipline cases by name and killed them outside their dormitory.
Turkana county commissioner Seif Matata said they exchanged fire with the killers but that they escaped.
He condemned the heinous act and asked residents to maintain calm as police investigate.
"This matter is very serious...police have launched a manhunt."
Red Cross, the county and a local NGO responded to the attack.
Those injured were taken to
Lopiding hospital and AIC health centre.
Story updated
