Fresh off a horrific 12-hour siege at a Somali hotel that left 17 dead, Islamist terror group Al-Shabaab has struck in Kenya, sending a squad of gunmen on a rampage through Garissa University College.

The attack has been in progress for eleven hours at the time of this writing, with CNN reporting heavy gunfire and explosions from the campus as security forces battle the terrorists. 550 people are still said to be missing. Reports on the university population vary, but it seems likely there were at least a thousand students and staff on site when the attack began.

Al-Shabaab has attacked Kenya before, most notoriously with the Westgate shopping mall massacre, and the university is only 90 miles from the Somali border, making it an accessible target. “The university was established in 2011 and is the only public university in the region,” writes CNN. “There are normally 800 students in the dormitories when school is in session, Jackstone Kweyu, dean of students, told Citizen TV. There are 1,000 staff members on a normal work day, he said. And there are usually four guards at the campus gates overnight.”

The attack began during morning prayers at 5 A.M. local time, as the kill squad shot the guards at the front gate, then moved on to the girl’s hostel, and then surrounded the on-campus mosque. There are about a dozen terrorists involved in the attack, clad in military fatigues and using heavy weapons. One of them was reportedly captured by security forces while trying to escape from the scene.

Many of the students fled during the attack, with hundreds taking refuge at a nearby Kenya Defense Forces camp. Several witnesses report the killers firing indiscriminately at students and teachers.

According to the UK Guardian, al-Shabaab spokesman Sheikh Abdiasis Abu Musab said his terror operatives released Muslim students and are holding Christian hostages on campus: “We sorted people out and released the Muslims. There are many dead bodies of Christians inside the building. We are also holding Christians alive. Fighting still goes on inside the college.”

Collins Wetangula, vice chairman of the student union at Garissa University, escaped from the slaughter after hiding with his roomates in their quarters. He confirms that Christians were targeted in the attack: “If you were a Christian you were shot on the spot. With each blast of the gun I thought I was going to die.” He also said the gunmen were shouting “We are al-Shabaab!” as they marched through the school.

The Guardian notes that separating out Christians for captivity and slaughter, while releasing Muslims, is standard procedure for al-Shabaab; they did the same thing during the Westgate massacre and other attacks.

The Kenyan government is portraying the university assault as a sign of desperation on al-Shabaab’s part, with one local politician declaring, “They are on the death bed. They need to be in the limelight – that is why they are going for these soft targets.” They’ve been hitting quite a few soft targets lately, and there have been reports that ISIS made diplomatic overtures to the al-Qaeda-linked Somali group, calling on them to carry out precisely the sort of attacks they’ve been perpetrating with such frequency.

Update, 12:30 PM EST: The death toll in the attack has skyrocketed to at least 70 killed, plus 79 wounded, according to the Associated Press. The siege is still ongoing. The Kenyan government says all staff members have been rescued from the university, and four of the attackers have been killed.

Update, 3:15 PM EST: The death toll has more than doubled, to 147, as the Kenyan government announced the siege was finally over. The UK Daily Mail says that some of the Christian students taken captive by al-Shabaab on campus were beheaded.