Long before his short stints in jail turned into years behind bars, Khalid Masood was known as Adrian Elms, with a reputation for drinking and an unpredictable temper. At least twice he was convicted of violent crimes, well before he stabbed a police officer to death Wednesday with a motion one horrified witness described as like 'playing a drum on your back with two knives.' But as he checked out of his hotel to head toward London for his deadly rampage, the manager said he was struck by his guest's friendly and outgoing manner. Within hours, Masood drove his rented SUV across the crowded Westminster Bridge, leaving a trail of dead and wounded. Then he jumped out and attacked the officer at Parliament with a blade in each hand, before being shot to death by police. In all, he killed four people and left more than two dozen hospitalized in what authorities called a terrorist attack. Masood, who at 52 is considerably older than most extremists who carry out bloodshed in the West, had an arrest record dating to 1983. The violence came later, first in 2000 when he slashed a man across the face in a pub parking lot in a racially charged argument after drinking four pints of beer, according to a newspaper account from the time. The victim, Piers Mott, would keep the scar the rest of his life, said his widow, Heather. The last conviction was in 2003, also involving a knife attack. It's not clear when he took the name Masood, suggesting a conversion to Islam. Heather Mott said Masood appeared to come out of jail 'even worse.' She said she got chills when she learned the identity of the London attacker. 'And it makes you feel even sicker when you think, God, that was the guy who lived here. What a pity they didn't realize he was a nutter,' she said. Police are combing through 'massive amounts of computer data' and have contacted 3,500 witnesses as they look for clues as to why the British-born man launched the deadly attack. 'Clearly that's a main line of our investigation is what led him to be radicalized: Was it through influences in our community, influences from overseas or through online propaganda? Our investigations and our arrests will help in that, but the public appeal will make a big difference if people come forward with more information,' said Britain's top counterterrorism officer, Mark Rowley. Prime Minister Theresa May said Masood was 'investigated in relation to concerns about violent extremism' years ago. But she called him 'a peripheral figure.' The Islamic State group described Masood as 'a soldier,' claiming responsibility for the attack. Rowley said police are investigating whether he 'acted totally alone inspired by terrorist propaganda, or if others have encouraged, supported or directed him.' Ten people remained in custody Friday on suspicion of preparing terrorist acts. Detectives have searched 21 properties in London, Brighton, Wales, Manchester and the central English city of Birmingham in one of Britain's biggest counterterrorism operations in years. Wednesday's attack was the deadliest in Britain since suicide bombers killed 52 commuters on London's transit system on July 7, 2005. Once Masood's identity became known, police and the media began tracing his final hours. The manager of the Preston Park Hotel in the beachside city of Brighton where Masood stayed the night before the attack said he seemed unusually outgoing and mentioned details about his family, including having a sick father. 'He was normal, in fact friendly, because we spent possibly five or 10 minutes talking to him about his background and where he came from,' Sabeur Toumi told Sky News. He was 'laughing and joking, telling us stories about where he lived,' Toumi said. Police raided the room, searching for clues about Masood. Among the items seized were the trouser press and the toilet paper holder. Masood's mother lives in rural Wales, according to a website on which she sells handmade creations like cushions and handbags. The listings on Folksy by Janet Ajao have been taken down, but in an archived version of the site, she describes living in 'rural west Wales with my husband, border collie and a few chickens.' Calls to the home in remote Trelech, Wales, went unanswered Friday. When Masood was in school, he took his stepfather's name, Ajao. He was athletic and popular in high school, known as someone who liked to party, according to Stuart Knight, a former classmate who said the young man was one of only two black students in the school of 600. 'I am in shock — that is not sympathy for what he has done — he was a nice guy and I'm surprised he turned and did what he did,' Knight said. In one of the last places Masood lived, a home in Birmingham, neighbors recalled him as a quiet man whose wife was veiled and who wore traditional Muslim clothing. But the neighborhood is not among one of the city's many Muslim enclaves, suggesting he was not deeply embedded in his religious community. Moazzam Begg, a former Guantanamo prisoner who was born and raised in Birmingham, said details emerging of the attacker's life raised questions about whether he had strong ties to the Muslim community and where he may have been radicalized. Since British authorities began cracking down on mosques, many people were instead being radicalized online, he added. 'He did not live in a Muslim neighborhood. In my mind, in my analysis, he was probably a drifter,' said Begg, adding that no one he knew in the community had met Masood. 'I'd also be surprised if he had any connection with a mosque, because sadly they are places where you can no longer discuss politics or air grievances.' Cultural and religious alienation can fuel such violence, he said. Begg helps run a group called Cage that has encountered extremists who spoke of their alienation before they committed attacks. Begg said his group did not know of any impending attacks. 'I've always felt negative radicalization is part push and pull,' Begg said. 'If a person feels like he doesn't belong ... this can be part of the push.' While in prison, Begg said he saw others who succumbed to radicalism. He said that groups like the Islamic State have exploited people's weaknesses and criminality. Further details of the London rampage continued to emerge Friday. A former British Army officer told the BBC that rescuers held the hand of Constable Keith Palmer and talked to him as they tried in vain to save his life after he was stabbed. Mike Crofts, a former Army captain who served in Afghanistan, said he was in the courtyard outside Parliament following a meeting with politicians about using boxing to engage young men when the attack took place. 'I rushed towards the scene,' he said, and began first aid along with Staff Sgt. Tony Davis, one of Crofts' instructors at Sandhurst, Britain's military academy. Ultimately, 20 to 30 people tried to save Palmer's life. 'Unfortunately, despite our best efforts, we were unable to save him,' Crofts said. 'Palmer at the time was surrounded by a whole host of colleagues who really loved him. We held his hand through the experience. We talked to him throughout, but unfortunately, he passed away.' ___ Hinnant reported from London, where Associated Press writers Danica Kirka, Jill Lawless and Gregory Katz contributed.