Spanish police say they've arrested four people in connection to terrorist attacks that killed 14 people and injured more than 100 others in and around Barcelona Thursday. Five suspects were killed as they tried to carry out a second terrorist attack in a nearby city.The current location of the driver of a white van that plowed through a crowd of people on Barcelona's landmark Las Ramblas boulevard Thursday afternoon remains unknown.Two brothers have been named in reports about the search for the perpetrators: Moussa Oukabir, a dual citizen of Morocco and Spain who was being sought by police along with three others Friday, and his older brother Driss Oukabir, who was arrested on Thursday.According to Spanish media outlets, Driss reportedly told police that Moussa, who's believed to be 17, may have stolen his identification. It was Driss Oukabir's name that reportedly appeared on rental papers for the van used in the attack. Moussa Oukabir lived in Ripoll, north of Barcelona, where his brother was arrested. He has no police record.Some reports have suggested Moussa Oukabir may have driven the van during the attack — but Catalan police said Friday evening, local time, "We continue to work to identify the driver" of the vehicle.Police believe that the attacks are the work of an organized group of terrorists — and that they acted after an accidental explosion derailed their plans to carry out a bombing in Barcelona.Police say three parts of eastern Spain are focal points of their investigation and that events in all of them are linked: Las Ramblas in Barcelona; the town of Cambrils, where a second vehicular attack took place; and Alcanar, where an explosion killed one person Wednesday night.Here's a roundup of the situation in Spain; we'll update this story with further developments Friday:SuspectsFour people have been detained by police — and none of them had "a history of terrorism-related events," police in Catalonia said Friday. They were detained in and around Ripoll, some 65 miles north and inland from Barcelona, according to police.Police arrested a Moroccan man whose "identification documents were used to rent the van" in the Las Ramblas attack, NPR's Frank Langfitt reports from Barcelona. That man, e was one of three suspects who held Moroccan passports; another suspect is a Spanish citizen, Catalan Police Chief Josep Lluis Trapero said Friday.Five men were shot and killed by police at a roadblock in Cambrils early Friday. They were wearing fake explosives on their bodies, police say.Trapero said investigators believe those who acted were survivors from a gang that had been planning for weeks to carry out a bombing attack — but that they decided to use a van after their components blew up.The Islamic State has claimed responsibility for the Barcelona attack, the SITE Intelligence Group reports.VictimsThe attack in Barcelona killed 13 people and injured more than 100. A woman who was injured in the later Cambrils attack has died, bringing the total number of victims to 14.The victims were from at least 34 countries — a reflection of Barcelona's popularity as a tourist destination. In addition to the U.S., the list ranges from Germany and Australia to Kuwait and Peru.At least one American died in the attacks, U.S. Secretary of State Rex Tillerson said Friday."We have now received word and confirmed the death of one American citizen in the terrorist attacks in Spain, amongst those who have been killed," Tillerson said."We express our deepest sympathies to the loved ones of this individual" and to others who suffered from the attack, Tillerson said.Suggesting there are other American casualties, Tillerson added, "We're still confirming the deaths and injuries of others."We have a separate story about those who were caught by the terrorist attacks.BarcelonaAt around 5 p.m. Thursday, a van sped down a pedestrian walkway, hitting scores of people.Barcelona resident Jordi Laparra, 55, witnessed the attack. He told the AP:" 'At first I thought it was an accident, as the van crashed into 10 people or so and seemed to get stuck. But then he maneuvered left and accelerated full speed down the Ramblas and I realized it was a terrorist attack. He zigzagged from side to side into the kiosks, pinning as many people as he could, so they had no escape."At noon Friday, Barcelona Mayor Ada Colau walked in the city's central plaza and led a moment of silence, saying she was doing so "with freedom and love for our city and our life."Gathered in the sunny Placa de Catalunya, a crowd clapped in unison and chanted, "I am not afraid," as they marched toward Las Ramblas, reclaiming the area from yesterday's violence."Kiosks are reopening on the promenade that was the scene of Thursday's terror attack," NPR's Soraya Sarhaddi Nelson reports. "Heavily armed police continue to block the area to vehicle traffic, and scores of tourists can be seen leaving area hotels in a hurry.""But the Barcelona airport this morning was packed with arriving passengers from around the globe, suggesting many vacationers refuse to be deterred by terrorism here."The head of the autonomous Catalan government here appealed for normality after what Spanish Prime Minister Mariano Rajoy described as a 'savage terror attack.' "Rajoy and other leaders, including King Felipe VI, attended the Barcelona rally.On Thursday, Colau said terrorism "will not stop us from being who we are: a city open to the world," with courage and solidarity.CambrilsAround 3 a.m. local time Friday, five men drove a car through a roadblock and plowed down a walkway along the beach in the resort town that is about 75 miles south of Barcelona."They hit pedestrians and a police officer, and then flipped the vehicle," Frank reports. "They got out of the car, they stabbed another pedestrian. Police shot and killed all five of these men, and they were wearing fake explosive vests."Four of the five suspected terrorists were killed by a single police officer, the Mossos police of Catalonia said Friday. The men had been armed with knives and an ax.Police have now identified three of the five suspects who were killed, local media report.AlcanarFarther south on Spain's eastern coast, a house exploded late Wednesday, possibly hastening the terrorists' plans for an attack, police said Friday. Police believe a jihadist cell was using the house as a location for making explosives. The blast leveled the structure.The explosion killed a person who police believe was making a bomb; five others were injured."The driver of the car in Cambrils, they say, is connected to that explosion," Frank reports, citing police.On Friday, police said they were moving a detainee who was seriously injured in the Alcanar explosion.AnalysisFrom NPR's national security correspondent Greg Myre:"Spain had been largely unscathed by Islamist extremism since the 2004 train bombing in the capital, Madrid, that killed more than 190. However, the Basque separatist group ETA has carried out mostly small-scale attacks for decades, and the Spanish security forces have considerable experience in dealing with terrorism."Deadly terror attacks in Europe have risen sharply since 2015, and that's largely because of ISIS, which has claimed responsibility for most of them. These have included highly orchestrated attacks, like the one in Paris in November 2015, where 130 people were killed when multiple ISIS terrorists carried out simultaneous assaults in the city."More recently, there have been several vehicle attacks in European nations, carried out by lone terrorists who apparently had little or no formal help from ISIS."ISIS began calling for vehicle attacks last fall, providing detailed instructions in its online magazine, Rumiyah, which means Rome. ISIS says it seeks to take over Europe, and Rome holds particular significance as the seat of the papacy."With reporting from Meg Anderson. Copyright 2017 NPR. To see more, visit http://www.npr.org/.