Two staff members were killed and several students were wounded in Kenya when gunmen fired on vehicles carrying students to the Technical University of Mombasa’s campus in coastal Kwale county on Tuesday, a police official and a witness said.

The identity of the gunmen was unclear.

Somali militant Islamist group al Shabaab frequently carries out attacks along the Kenya-Somali border and along the Kenyan coast. In 2015, it attacked a university in Kenya’s Garissa town, killing 148 students.

Two female staff members were killed Tuesday’s attack, and a driver and two policemen were injured, a police official who did not want to be named told Reuters.

“A bus carrying students of TUM (the Technical University of Mombasa) was ferrying them from their hostels to the campus in Ukunda for classes and was being escorted by a van that had some staff of the college and two escort police officers,” the policeman said.

“Armed men numbering about 10 emerged from the bushes and started firing at the van in front. As a result two ladies who are staff of TUM were killed in the van. The driver of the van and two police officers were injured,” he said.

A witness who did not want to be named told Reuters she and several other students had fled their vehicle when gunmen opened fire on them and had seen several students covered in blood.