March 24, 2017 6:57 p.m. ET
BRIGHTON, England—On Tuesday, Khalid Masood ate a takeout kebab for dinner and spent his last night alive alone in a small, budget hotel in this English seaside town. He checked out before 8 a.m. the next morning, like anyone else with plans for the day. “He just put the key on the counter and left,” the hotel’s receptionist said.
Hours later, police say, Masood went on a rampage 50 miles to the north in London—mowing down pedestrians with his car, killing three, before leaping from the vehicle and stabbing an unarmed policeman to death outside the British Parliament. Police then shot and killed Masood.
In the days before the attacks, Masood, a 52-year-old British convert to Islam, crisscrossed the country, traveling from Brighton on the south coast to the central city of Birmingham and back before aiming himself at the heart of the capital to undertake the last acts in an itinerant life punctuated with violence.
On Friday, police and intelligence officers were still trying to assemble the elements of Masood’s confusing story and decipher his motives. Born Adrian Elms in southeast England, he used multiple names and aliases, police said.
He changed addresses regularly, appearing in recent years to move among places that have had connections to extremist plots. He had multiple criminal convictions—the first when he was still a teenager—and served jail time.
Since Wednesday’s terrorist assault, the worst in Britain since a series of coordinated bombings in 2005 killed 52 people, hundreds of detectives have worked to trace Masood’s movements and associates.
After a series of raids on locations connected to Masood, police on Friday were holding four people on suspicion that they were preparing terrorist acts. A fifth person was released from custody on bail.
“Our determination is to find out if either he acted totally alone, inspired by perhaps terrorist propaganda, or if others have encouraged, supported or directed him,” said Mark Rowley, deputy commissioner of the London Metropolitan Police.
A British intelligence official said authorities were looking into whether Masood became radicalized while in prison, an increasingly common path to terrorism. The official also said it was unclear what role several trips Masood made to Saudi Arabia had played.
“We’re trying to piece together what we can,” the official said. “The big question is at what point did he decide to do this and why, and who else is involved.”
Extremist group Islamic State this week said Masood was one of its “soldiers” and claimed responsibility for the attack. But the intelligence official said authorities had found no evidence Masood was linked to or had communicated with Islamic State.
It wasn’t clear when he became a Muslim. Prime Minister Theresa May said earlier this week that Masood had been investigated years ago in connection with extremism, but had been deemed a “peripheral figure.”
Long stretches of Masood’s life are difficult to account for. He was born on Christmas Day in 1964, according to police. He attended high school in Kent, southeast of London. By the late 1990s, when Masood was in his 30s, he had landed in the quiet village of Northiam in nearby East Sussex.
At the time, he was still using the name Adrian Elms. People who knew him said he worked at a small family-owned business called Aaron Chemicals and went by the nickname Aidy. He wasn’t known to practice Islam. But amid these signs of a conventional life, there were signs of internal turmoil.
“He was a normal guy until he had a couple of drinks,” said Nigel Gill, who runs a local convenience store and used to sell beer to Masood. Mr. Gill said Masood once attacked a woman’s car with a baseball bat after an argument.
In 2000, Masood lashed out again. Heather Mott said her late husband, Piers, the owner of a local cafe, was in a pub then called the Crown and Thistle when Masood started an argument with another customer. Mr. Mott stepped in.
An angry Masood attacked her husband with a knife, Mrs. Mott said. The assault left a 3-inch gash on Mr. Mott’s face, according to a report of the court proceedings published that year in the local newspaper, the Argus.
A lawyer for Masood argued there were “racial overtones” to the dispute, the Argus said. Masood’s mother is white, his father black. Masood was sentenced to two years in prison.
Adrian Baker, who owns a carpet shop next to the pub where the attack took place, said he would cross the road to avoid walking past Masood. “You could tell he was a bit of a troublemaker,” he said. After the knife attack, Masood “just disappeared,” Mr. Gill said.
Masood went to Saudi Arabia after he was released from prison. The Saudi Embassy in London said Masood was in Saudi Arabia on a work visa to teach English from November 2005 to November 2006 and again from April 2008 to April 2009.
In 2015, he obtained a pilgrimage visa through a travel agent and was in the country in March of that year, the embassy said. “During his time in Saudi Arabia, Khalid Masood did not appear on the security services’ radar and does not have a criminal record in the kingdom of Saudi Arabia,” the embassy said.
Katie Garricques, who lives in Luton on the outskirts of London, said she recognized Masood from a police photo as her neighbor for a couple of years around 2010 and 2011. He lived there with his wife, who wore African attire, and two children, she said, adding he worked frequently in the garden. She said they would exchange hellos.
“He was very fatherly and loving and I was quite shocked. There was never any indication that he’d be radicalized or aggressive,” she said. “I felt sickened.”
Masood’s time in Luton, home to a large population of Muslims, coincided with bursts there of political and sectarian ferment. At around that time, a man named Junead Khan was also living in Luton. Mr. Khan was later convicted of preparing a terror attack in connection with a plan to kill Royal Air Force personnel. Mr. Khan posted a video on YouTube in those years showing himself listening to music that features in some ISIS propaganda while driving across the Westminster Bridge, scene of Masood’s attack this week.
Later, Masood seems to have moved to Birmingham, a city with a history of connections to terror. Since the Wednesday attack, police have searched a series of addresses in the city and detained two people there.
Ciaran Molloy and other neighbors said they recognized Masood as a previous occupant of one of the houses being searched from a photo circulated in the media. They said he lived there with a woman and small children and rarely spoke to other residents on the quiet street.
Several neighbors said that Masood occasionally dressed in traditional Muslim attire—a white robe and a skullcap—while his wife always wore a head scarf but didn’t cover her face.
Fernando Costa, a 46-year-old auto mechanic from Portugal, said his interactions with Masood amounted to regular neighborly banter—questions of lawn mowing, driveway parking, and the weather. “I’d never think this guy could do something like this,” Mr. Costa said.
Masood and his family lived on the street for at least three years, several neighbors said, and left just before Christmas. “It was pretty sudden,” Mr. Molloy said.
Last Friday, St. Patrick’s Day, Masood checked into the Preston Park Hotel in Brighton late in the evening, according to the hotel receptionist, and left early the next morning.
By the start of the week, Masood was back in Birmingham, where he rented a gray Hyundai Tucson compact SUV at an Enterprise Rent-A-Car in a dingy industrial park about a mile from the house where neighbors said he once lived.
He drove it back to Brighton and returned to the Preston Park. The receptionist said he spent most of Tuesday in his room. He paid by credit card and didn’t make any phone calls, before leaving the next morning, bound for London and mayhem.
—Joshua Robinson, Margot Patrick, Joanna Sugden, Wiktor Szary, Mike Bird, Laurence Fletcher and Justin Scheck
Khalid Masood was born Adrian Elms. The headline on an earlier version of this article incorrectly stated he was born Adrian Alms. (March 25)