The Kampala bombings were a watershed, says East Africa human rights and security investigator Clara Gutteridge. Suddenly, “East Africa was a new front in the global war on terror.” F.B.I. agents arrived in Kampala hours after the attacks, according the U.S. ambassador to Uganda Jerry P. Lanier, and immediately they caught a break. Somehow – maybe the bomber lost his nerve, maybe his device malfunctioned – a third bomb planted in a nightclub did not detonate. A cleaner found the device in a laptop bag the following morning leaning against a wall near the bar. Also in the bag was a cell phone.

The F.B.I. agents hacked the phone’s SIM card, used its call history to plot a network of numbers, repeated the process with those numbers and within hours had constructed a phone tree connecting more than 100 people in Uganda and Kenya to the bomb. Then they handed their work to their counterparts from Uganda and Kenya.

Eleven days after the attacks, at 3:30am on July 22, Mohamed Abdow, a 24-year-old street hawker and an ethnic Somali Kenyan, and his brother were sleeping in their shack in the market town of Tawa, east of the Kenyan capital Nairobi, when there was a knock at the door. In interview with TIME, Abdow said he opened the door to find 20 men, some in police uniform, some in civilian clothes. They pushed past him. “They ask for our phones,” said Abdow. “My phone is under my mattress so I ask my brother to call it. I say, ‘0…7…2…4…,’ and as soon as I mention those digits, one man says, ‘That’s the number we’re looking for’ and they tell us to lie down on the floor, tie our hands behind us and say: ‘If you get up, we will shoot.’ Then they ransack the house as two officers hold guns to our heads.”