What you need to know:
- Interior ministry names him as Abdirahim Abdullahi, a university of Nairobi law graduate.
- Abdullahi was one of the four dead Al-Shabaab gunmen who massacred nearly 150 people at Garissa University College.
One of the Garissa attackers has been identified as a Kenyan national.
Interior ministry spokesman Mwenda Njoka named the attacker as Abdirahim Abdullahi, saying he was "a university of Nairobi law graduate and described by a person who knows him well as a brilliant upcoming lawyer."
The spokesman said Abdullahi's father, a local official in Mandera County, had "reported to the authorities that his son had gone missing and suspected the boy had gone to Somalia".
Describing Abdullahi as a high-flying A-grade student, Njoka said it was "critical that parents whose children go missing or show tendencies of having been exposed to violent extremism report to authorities".
Abdullahi was one of the Al-Shabaab gunmen involved in the massacre at Garissa University College during which non-Muslim students were lined up and executed.
The massacre, which was the deadliest attack on Kenyan soil since the 1998 bombing of the US embassy in Nairobi, claimed the lives of 142 students, three police officers and three soldiers.