Nobody wants to talk about Abdelbaki Es Satty. When pressed, those who knew him call him “evil” and “savage” and a disgrace to the communities he’s lived in. Some of his neighbors are just surprised that the imam next door was capable of masterminding an attack. But most of his acquaintances from recent years didn’t know his past: that he’d been investigated and had his phone tapped in one of the largest international terrorism cases in Spanish history; that he had two smuggling convictions and had spent four years in prison. Despite all that, he was able to live under the radar while he organized the most deadly terrorist attack in Spain since the 2004 Madrid train bombings.

The Spanish government especially does not want to talk about Es Satty. The investigation into his case is sealed by a judge. Spanish police won’t offer much comment on the case, nor will police for the region of Catalonia, of which Barcelona is the capital. The director of Spain’s intelligence agency — referred to as the CNI, for its initials in Spanish — has given one closed-door briefing on Es Satty in the Spanish Parliament, and did so only after politicians began calling for a public investigation.

And so, over a year after the attack, the public has been provided few answers as to how Es Satty was able to convince a group of young men to kill and injure innocent people on a mass scale — and how he evaded police attention while doing so.

On the afternoon of August 17, 2017, a white rental van careened down Las Ramblas, a pedestrian avenue in Barcelona, full of restaurants, souvenir shops, street sellers, and tourists — something like Barcelona’s Times Square, but stretched out, three-quarters of a mile long, to connect two of the city’s major landmarks. The driver made sure to zigzag through the crowds that day in order to strike as many people as possible. He killed 15 and injured over 130. After driving for about half the length of Las Ramblas, the driver, 22-year-old Younes Abouyaaqoub, ducked out of the van and fled on foot until he hijacked a car at knifepoint and stabbed the driver to death. Abouyaaqoub forced his way through a police checkpoint, running over an officer as he fled. Police later found the car left in a town on the outskirts of Barcelona, with the body of the car’s owner still in the backseat. That night, TV news announced that the killer from Las Ramblas was still on the loose.Just after midnight, a black Audi sedan with five people inside drove through a crowd of people in Cambrils, a beach town 75 miles away from Barcelona. They struck seven people, one of whom would later die from her wounds. The car eventually flipped at a traffic circle. When the five exited the car, four were shot on the spot by police. The fifth person fled and was later shot.

Four days later, police were tipped off to Abouyaaqoub’s location: Subirats, a small town 30 miles outside Barcelona. Police said that when they found Abouyaaqoub, he was wearing an explosive belt. They shot him to death. The explosive belt turned out to be fake. Police and the press noted that Abouyaaqoub shouted “Allahu akbar” before being shot.

Within a week, eight suspected members of the cell behind the attack were dead, and four were in police custody in Spain. Two more suspects were detained in Morocco. The press called the police response a success.

Es Satty was dead, but the discovery of his backstory was just beginning.