Although security agencies have not said whether they knew the details of the planned attack, the college is said to have asked for more security.
From last weekend, four Administration Police officers were sent to guard the hostels. They were the first to respond when the attackers struck, according to Interior Cabinet Secretary Joseph Nkaissery.
The group said at the time that it was avenging the killings of Muslims in Kenya and in Somalia where Kenyan troops are trying to flush out the militants.
Even though Garissa University College is the only public university in northern Kenya, it has never been at risk of a terrorist raid despite the town having been attacked 11 times before.
But that is until Al-Shabaab discovered it was one of the few public places where Kenyans of different ethnic groups gather daily.
