Around 5:30 Thursday morning, when Hassan Osman, a 35-year-old newlywed and an employee with Kenya’s Ministry of Health in Garissa, was in the mosque praying, he heard the sharp report of rapid gunfire rip through the still morning air. 

The noise came from the direction of nearby Garissa University College. There, gunmen had forced their way into the campus, shooting guards standing sentry at the main entrance and opening fire indiscriminately.

Eyewitnesses on the scene earlier report that “seven to 10 heavily armed attackers masked from head to toe” stormed the college in this moderate-sized city in northeast Kenya, two-thirds of the way from Nairobi to the border with Somalia.

Al Shabaab has claimed responsibility for this latest attack inside Kenyan territory—one of scores the Somali militant organization has launched since Kenya’s 2011 incursion into Somalia, including the bloodbath unleashed on September 21, 2013 at Nairobi’s Westgate shopping mall.

Shabaab’s spokesman, Sheikh Mohamed Ali Rage, gave no specific numbers on fatalities and injuries but said to the BBC, “We’ve killed many people; Kenyans will be shocked when they go inside.”

And Kenyan security forces told reporters they’d “only just begun” to “mop up.” 

Osman and other residents never imagined an attack in Garissa town. The majority of its 120,000 inhabitants are Muslims of Somali origin. But if the attack comes as a surprise to locals, it didn’t come as such to the residents of Kenya’s capital, who’d been warned last week of impending attacks on institutions of higher education. 

According to a VOA report, the University of Nairobi warned its students last week that Al Shabaab was planning attacks on a “major university.”

Kampalans received similar warnings before the public prosecutor in the trial of suspects in the 2010 Al Shabaab World Cup bombings in Uganda was shot dead last week.

Easter weekend is coming up. The attack comes one day after the one-year anniversary of the assassination by Kenya death squads of Sheikh Shariff Makaburi in Mombasa. Makaburi was an avowed recruiter for Al Shabaab.

Security forces responded to the Westgate attack by unleashing their own fury at Kenya’s Muslim communities. Retaliation has taken the form of raids on mosques, mass arrests, crippling curfews and targeted assassinations like that of Makaburi’s predecessor Aboud Rogo and dozens more. 

In further retaliation, Al Shabaab then carried out the Mpekatoni attack, killing more than 60 in that Kenyan coastal town last June. 

While security analysts say Al Shabaab is being weakened in Somalia, others insist that the militant group is gaining ground in Kenya.

“With Garissa, Al Shabaab outsmarted intelligence services again,” says Professor Paul Goldsmith, an American security and conflict analyst at Kenya’s Coast International University. “And they chose a target that’s significant on impactable terms—to polarize Christians and Muslims while exacerbating longstanding tensions between the regions Somali communities and the Kenya government.”

Meanwhile, in Eastleigh, a Nairobi suburb where thousands—mostly women and children—were detained last April in a police sweep, many are glued to television sets, wondering how police will respond next. 

At last count, 12 hours after the attack at Garissa University, the total number of fatalities had risen to 147.

If security forces, foreign and domestic, have the final say, pulling Kenya’s troops out of Somalia is not an option.

“The best place to stop Al Shabaab is on our border,” says Andrew Franklin, former U.S. Marine, now a security consultant. “We need to prioritize controlling the border with Somalia.”

After the Mandera attack in December, it’s increasingly held that constructing a wall is the answer, as Israel, Egypt, Morocco, the U.S., and most recently Saudi Arabia (in sealing itself off from Yemen) have tried. 

Is a wall between Kenya and Somalia next?

“We are in an awkward situation,” said Osman. “Ethnically we are Somali, religiously we are Muslim. But the sentiments we share with the Kenyans are that Al Shabaab should not be killing innocent Garissa residents. Garissa is happy to be a part of Kenya.”