British media have identified the suspect held in connection with the van attack outside a London mosque as Darren Osborne, from the Welsh city of Cardiff. He is being held on suspicion of attempted murder and alleged terror offenses. British media report that some of Osborne's neighbors have described the father of four as "aggressive" and "strange." Witnesses said Osborne claimed he wanted to "kill all Muslims" after he drove into a crowd leaving a mosque early Monday morning. One man who was receiving first aid at the time of the attack died; it's unclear if his death was a result of the attack or from a previous condition. Osborne was arrested on suspicion of the commission, preparation or instigation of terrorism including murder and attempted murder. Police believe the suspect acted alone and searches were being conducted at a residential address in the Welsh capital. Police are treating the incident as a terror attack and British Prime Minister Theresa May described it as "sickening," vowing on Monday to fight extremism in all its forms. The string of attacks had "bruised but not broken the heart of this great nation," Home Secretary Amber Rudd said. The attack raised fears of retaliation against Muslims after a series of deadly assaults in Britain by militants. One man who was already receiving first aid at the time died following the assault, while nine people were taken to hospital and two others were treated for minor injuries. Londoners bearing flowers and messages of solidarity gathered late Monday at the scene of the attack, some carrying signs reading "United Against All Terror." Another vigil is planned for Tuesday. The van driver was pinned down by locals before being shielded from retaliatory violence by an imam and detained by police. The man suspected of driving the van was arrested on suspicion of "the commission, preparation or instigation of terrorism including murder and attempted murder," police said. London police chief Cressida Dick said the incident was "quite clearly an attack on Muslims" and promised a stepped-up police presence near mosques as the holy month of Ramadan draws to a close. Rudd said Muslims needed to feel safe in Britain and the government was working to tackle all forms of hate crime and extremism. "Indicative figures suggest that over half of those who experience hate because of their religion are Muslim. Any hate crime is unacceptable but this stark figure is something we will not shy away from," she wrote in The Guardian newspaper. "We stand with the Muslim community — you are not alone, we share your pain and we will not let you down." One victim of Monday's attack has no memory of what happened, according to a nephew who did not wish to be identified. "He is bleeding out of his ear, but in general his health was stable," he said after visiting his uncle Hamza Sharif in hospital. "He has a fracture in his skull — but they still don't know why the bleeding from his ear is not stopping yet," the Somali-born man said. Sharif "does not remember anything" of the attack and kept asking "what was wrong." — Agencies