Authorities in Kenya said Sunday they have identified one of the four dead Shebab gunmen who massacred nearly 150 people at Garissa University as an ethnic-Somali Kenyan national and law graduate.

Interior ministry spokesman Mwenda Njoka named one of the attackers 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 the northeastern county of Mandera, had "reported to the authorities that his son had gone missing and suspected the boy had gone to Somalia".

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Attack at Garissa University in Kenya

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."

Somalia's Al-Qaeda-affiliated Shebab militants claimed responsibility for Thursday's massacre at Garissa University, 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.

Although losing ground in Somalia, the Shebab have stepped up attacks inside Kenya as well as its recruitment of Muslim youth in the country's northeastern and coastal regions.