NAIROBI, Kenya — Al-Shabab gunmen attacked a college in northeast Kenya early today, targeting Christians and killing at least 15 people and wounding 60 others, witnesses said. The president said it is now a hostage situation.

Even as security forces cornered the gunmen in a dormitory at Garissa University College where they could be holding hostages, survivors described to The Associated Press a harrowing scene, where people were mercilessly gunned down and bullets whistled through the air as they ran for their lives.

Collins Wetangula, the vice chairman of the student union, said he was preparing to take a shower when he heard gunshots coming from Tana dorm, which hosts both men and women, 150 yards away. The campus has six dorms and at least 887 students, he said.

He said that when he heard the gunshots he locked himself and three roommates in their room.

“All I could hear were footsteps and gunshots nobody was screaming because they thought this would lead the gunmen to know where they are,” he said.

When the gunmen arrived at his dormitory he could hear them opening doors and asking the people who had hidden inside whether they were Muslims or Christians.

“If you were a Christian you were shot on the spot,” he said. “With each blast of the gun I thought I was going to die.”

The gunmen started to shoot rapidly and it was as if there was an exchange of fire, he said.

“The next thing, we saw people in military uniform through the window of the back of our rooms who identified themselves as the Kenyan military,” Wetangula said. The soldiers took him and around 20 others to safety.