(CNN)Gunmen raided a Kenyan university early Thursday, killing students and taking others hostage during morning prayers.
Kenya terrorist attack: 6 things you need to know
Al-Shabaab, the Somalia-based Islamist militant group, has claimed responsibility. Here are a few early takeaways from the terror attack.
The university is in Garissa in eastern Kenya, 90 miles (145 kilometers) from the border with Somalia. The town is mostly ethnic Somali, said CNN's David McKenzie, and Al-Shabaab has terrorized the region in recent years with grenade and machine gun attacks.
From the Beslan siege in 2004 to the Peshawar academy attack in December, it is clear that terrorists now see schools -- and children -- as easy targets for headline-grabbing attacks, terrorism expert Sajjan Gohel said.
"Terrorists deem these institutions as soft, symbolic targets where they're able to get the oxygen of publicity, attract notoriety and spread the fear factor," he told CNN.
Joel Ayora, who was on the campus and witnessed the attack, said gunmen burst into a Christian service. Taking hostages from the service, they then "proceeded to the hostels, shooting anybody they came across except their fellows, the Muslims."
The attackers separated students by religion, allowing Muslims to leave and keeping an unknown number of Christians hostage, Agence France-Presse reported.
Persecution of Christians is a growing problem in Kenya, according to Open Doors UK, an international ministry. In 2014 Kenya shot up to 19th (from 43rd) in the group's rankings of the top 50 countries where persecution of Christians is most severe, according to the group's website.
The security situation may have deteriorated in recent years after Kenya's incursion into Somalia to battle Al-Shabaab, McKenzie said.
Kenya wiped out some of the group's key bases there, but it made the group more diffuse -- and more likely to pop up and hit soft targets in neighboring countries, including Kenya, Gohel says.
It doesn't help that the border between the countries is porous, Gohel says, and security can be inconsistent and even lax at times.
It's also simply very difficult to protect every single target from attacks -- especially in Kenya, Gohel says, "where the security is such that it will be impossible to provide adequate security throughout the country."
Adan Garaar, mastermind of Al-Shabaab's deadly raid on Nairobi's Westgate mall in 2013, was reportedly killed last month in Somalia by a U.S. drone strike. But the group hasn't missed a beat.
In November, it ambushed a bus in Kenya, killing everyone who couldn't recite verses of the Quran. Last week, the group raided a hotel in Mogadishu, killing a Somali diplomat and others. And earlier this week, Uganda's lead prosecutor in the trial over an Al-Shabaab massacre in Kampala in 2010 was shot dead, according to The Guardian.
"This is an uphill treadmill for counterterrorism," Gohel says. "For every individual killed, there are at least another five coming down the assembly line."
Kenyan security forces were criticized for their handling of the Westgate massacre, but Gohel says the country will need a lot more help from its neighbors and the U.S. to contain the group.
"Al-Shabaab is not just a local terrorist group, it's a transnational outfit," he says. "It operates throughout a number of countries and recruits even people from the West."
Last month, the U.S. Embassy warned of possible attacks "throughout Kenya in the near-term" after reports of Garaar's death, but there was no information about a specific place thought to be under threat.
McKenzie says Al-Shabaab is trying to maintain its relevance as other terror groups like Boko Haram, ISIS and al Qaeda in the Arabian Peninsula vie for power and influence.
McKenzie says it's also possible that Al-Shabaab may have abandoned aspirations of seizing a large chunk of territory after taking losses in Somalia, and decided instead to focus purely on terrorism.
It's also hard to know what shape the next attack will take. "You could have assassinations one day, you could target an institution the next day, and it's impossible to stop," Gohel says.
"These attacks are cost-effective," he says. "If the group's infrastructure and resources remain intact in Kenya, we will see more attacks taking place. This is not a one-off incident."