The police have released the first image of Westminster killer Khalid Masood and are appealing for more information on the man reportedly nicknamed "the Vampire" by neighbours.

School images of Masood have been published, while his birth name is revealed as Adrian Russell Ajao. He also went by the name of Adrian Elms.

Masood reportedly was on WhatsApp minutes before his rampage on Wednesday.

He had a long criminal history, once stabbing a man in the face, and MI5 knew he was a terrorist sympathiser.

His neighbours, however, saw only a quiet family man who took care of his garden.

LONDON — The Metropolitan Police has released the first official image Khalid Masood, the man behind the brutal attack on Westminster, London, on Wednesday.

Masood, 52, was born in Kent, grew up in Rye, East Sussex, and had previously been investigated by MI5 over concerns relating to violent extremism. His birth name was Adrian Russell Ajao, while he also called himself Adrian Elms, the police said.

While authorities said they were not aware he was planning Wednesday's attack, the police indicated in a statement on Thursday that he had a string of previous convictions from 1982 to 2003. The married father of three was never convicted of any terrorism offences.

The force appealed to the public for more information on Masood.

School photos and WhatsApp messages

The BBC and The Sun published other images of Masood on Friday afternoon. The photos show Masood with his football team at secondary school in Tunbridge Wells and in a posed image with classmates.

—BBC Breaking News (@BBCBreaking) March 24, 2017

Sky News and MailOnline have also reported that Masood was active on the Facebook-owned internet messaging service WhatsApp just minutes before the attack on Westminster Bridge.

Screenshots show he had "seen" his messages at 2:37 p.m. on Wednesday, just three minutes before he drove a vehicle through pedestrians on the bridge. His messages were encrypted, but the police are believed to have seized his cellphone.

Mark Rowley, the acting deputy commissioner of the Metropolitan Police, said the police were trying to determine whether Masood acted "totally alone" or was inspired by terrorist propaganda or whether anyone "encouraged, supported, or directed him."

Mark Rowley, the acting deputy commissioner of the Metropolitan Police. PA

"At this point, I want to appeal specifically to the public," he said on Friday. "We remain keen to hear from anyone who knew Khalid Masood well; understands who his associates were; and can provide with information about places he has recently visited."

The police have not linked Masood to a terrorist organisation. ISIS, the terrorist group also known as the Islamic State, ISIL, or Daesh, claimed responsibility for the attack, in which five people including Masood were killed and at least 40 others were injured. ISIS did not name Masood in its statement released to Amaq, the news agency linked to the group.

Masood was not named for more than 24 hours as the police investigated the attack. In the early hours of Thursday morning, the police raided six addresses in London and Birmingham in connection with the investigation and made eight arrests.

Two further "significant" arrests were made Thursday night, and nine people remain in custody, the police said.

Aysha Frade and Kurt Cochran, two of the people who were killed by Masood's car. Sky News/Facebook

PC Keith Palmer, a British police officer; Aysha Frade, a Spanish-born college worker; and Kurt Cochran, an American tourist, were killed in the attack. A fourth victim, a 75-year-old man named Leslie Rhodes, was named Friday morning. Two people remain in hospital in a critical condition, one with life-threatening injuries.

Record of convictions

In a statement, the Met Police said Masood was born in Kent on December 25, 1964. He was living in the West Midlands, the police confirmed.

The Birmingham Mail said he recently lived at a Quayside address in Birmingham city. The newspaper also reported that he left a Winson Green property in December. Winson Green is an area in the west of the city of Birmingham and is near HM Prison Birmingham and City Hospital.

The police raided a flat on Hagley Road, Birmingham, on Wednesday night. PA

Masood was well known to the police for a string of convictions from 1983 to 2003. These included grievous bodily harm, possession of offensive weapons, and public-order offences.

The Times said Masood spent time in Lewes jail in East Sussex, Ford open prison in West Sussex, and Wayland prison in Norfolk.

His last conviction was for possession of a knife in 2003. The Mail suggested that was a turning point for Masood:

"His last was for an attack in 2003, where he stabbed a 22-year-old man in the face, leaving him slumped in the driveway of a nursing home in Eastbourne. The victim was left needing cosmetic surgery after the vicious attack.

"He was later charged with GBH, wounding with intent and possessing an offensive weapon.

"It is understood he was jailed for the attack and it is thought his indoctrination may have begun through meeting extremists while in prison."

The police said he had not been convicted of any terrorism offences.

Prime Minister Theresa May did say, however, that in addition to his encounters with the police, Masood was investigated by MI5 "in relation to concerns about violent extremism."

A quiet, bodybuilding English teacher

Masood's rented 4x4 car outside the UK Parliament. Luke Steele / Twitter

Other details about Masood's life are emerging.

The Times reported that Masood was born in Dartford, Kent, and was raised by a single mother in the picturesque seaside town of Rye, East Sussex.

After a religious conversion, the Met Police said, Masood (born Adrian Russell Ajao) went by multiple names, with Sky News also identifying him as Khalid Choudary.

He was a married father of three, according to reports in the British press.

The Sun obtained a résumé it said Masood distributed just weeks ago. The document reportedly said he worked in Yanbu, Saudi Arabia, teaching English to workers at the General Authority of Civil Aviation beginning in 2005. He also reportedly said he had an economics degree.

The Department of Education, however, told the BBC that Masood was not certified to teach English in the UK, though he apparently called himself an "English tutor."

Masood after the attack. PA A source who met him in a professional capacity told Sky News that Masood was "a big bloke, he looked like he was a bodybuilder, wouldn't want to mess with him."

A neighbour described him as a "quiet man." She told the Birmingham Mail that she often saw him washing his car and mowing his lawn when he lived in Quayside.

Another neighbour told The Mail that he took care of his garden:

"Neighbour Iwona Romek, 45, said: 'When I saw the pictures on TV and in the papers of the man who carried out the attack, I recognised him as the man who used to live next door.

"'I would see him quite often, but it would just be a "hello" and a "how are you". He had a young child, who I'd think was about five or six years old.

"'There was a woman living there with him, an Asian woman. He seemed to be quite nice, he would be taking care of his garden and the weeds.'"

The Independent reported a similar picture:

"Shocked residents in Winson Green, described a man who had appeared the perfect suburban neighbour.

"'He washed his car, mowed his lawn,' said Ciaran Molloy, 27, a mailing machine engineer who lived overlooking Masood's new-build house. 'He was quite friendly, polite in every interaction.'"

'The Vampire' ... a 'nice man' who wants a discount

The Mirror reports that neighbours nicknamed him "the Vampire" because he would "frequently" go out at night dressed in black.

According to The Sun, he stayed at a £59-a-night hotel ($74) in Brighton on Tuesday night, telling workers before he left on the day of the attack that London "isn't what it used to be." Masood checked in at the Preston Park guest house on Friday night and then again on Tuesday night:

"A source said: 'On both occasions he was asking for a cheaper rate. You would have thought if you were hellbent on committing a terror attack you'd chuck it all on a credit card and forget the cost."

"Staff liked him so much they even wrote 'nice man' on his computer booking."

The Hyundai 4x4 car he used to mow down pedestrians on Westminster Bridge was rented from Enterprise in Birmingham, according to reports.

How the attack on Parliament unfolded

At about 2:40 p.m. local time on Wednesday, an assailant drove a 4x4 car along Westminster Bridge — crowded with tourists — and hit many pedestrians.

The driver then crashed the vehicle into railings near the houses of Parliament before entering the grounds and fatally stabbing Palmer. The BBC and Sky reported that the man, now identified as Masood, was shot dead by Defence Secretary Michael Fallon's security guard.

A plain-clothed officer was pictured standing over the attacker with his gun.

Masood was sprawled just metres away from Palmer.

The attacker was stripped and searched, presumably for explosives, before being loaded into an ambulance. He died from his gunshot wounds.