According to CNN, the gunmen at Garissa University College were "firing indiscriminately and sending students scrambling for cover." The Kenya Red Cross reported at least 30 hospitalized, mostly from gunshot wounds. Reuters via NBC News reported two security guards had been killed in the midst of explosions and bullets, 30 hospitalized with four in critical condition.

"Two guards who were manning the gate at the university have been killed," a police officer told Reuters. "We can hear gunshots from inside the compound but at this point we can't tell who is shooting at who or what."

It is unclear if hostages were taken by the masked gunmen, but according to Reuters, the standoff lasted for hours. No clear reports of a resolution have been issued at this time.

Gunshots were heard "like fireworks" starting at 5 a.m. local time - the hour of morning prayers, a witness told CNN. "We don't know how many (shooters) there were, but there are probably more than 10," Robert Alai Onyango, a blogger in Nairobi, told CNN. "We believe the attackers were wearing something close to military fatigues."

The shooters seemed to shoot indiscriminately and "basically from all angles," Onyango told CNN. "They surrounded the mosque ... we don't know why they were surrounding the mosque."

Newspaper journalist Steven Astariko told CNN that 300 students sought refuge at a Kenya Defense Forces camp.

Garissa is located about 90 miles from the Kenya-Somalia border. No one has claimed the attack, but Al Qaeda-linked al Shabaab has been known to attack from within Kenya to punish the country for sending troops into Somalia to fight al Shabaab militants.