London police name Parliament attacker as British-born Khalid Masood, age 52

We have made 7 arrests: London's Met Police
We have made 7 arrests: London's Met Police

London police have released the name of the man who killed three people and injured 40 before he was shot to death in a suspected lone wolf terror attack on the Houses of Parliament.

One of those killed was an American who was visiting with his wife on their 25th wedding anniversary.

Khalid Masood, 52, was born in Kent in 1964 and was believed to have most recently lived in the Midlands, the Metropolitan Police said in a statement Thursday.

While Masood was not the subject of a current investigation and there was no sign that he was about to mount an attack, he was known to police, the statement said. Masood had a range of previous convictions to his name including assault and possession of offensive weapons.

Police said his first conviction was in November 1983 for criminal damage and his last was in December 2003 for possession of a knife.

Earlier, British police had searched six addresses and made eight arrests in raids as part of an investigation into the Wednesday's attack, which left four people.

Masood plowed his car into pedestrians on London's Westminster Bridge and then fatally stabbed a police officer before being shot to death. Police had said five died but they revised it to four overnight.

Late Thursday, police said a 75-year-old man injured in the attack died after his life support was withdrawn.

@metpoliceuk: Detectives investigating the terrorist attack in #Westminster can confirm that a 75yo man died tonight after his life support was withdrawn.

In a statement to the House of Commons earlier on Thursday, Prime Minister Theresa May gave details of the casualties' nationalities on top of the 12 injured Britons: One American, three French children, two Romanians, four South Koreans, one German, one Pole, one Irish, one Chinese, one Italian and two Greeks.

An official from the Mormon church in Utah identified the slain American as Kurt W. Cochran, who was on a wedding anniversary trip to London with his wife, Melissa. She was seriously wounded, The Associated Press reported.

Later Thursday the Islamic State group said through its Aamaq News Agency that the attacker was a soldier of the Islamic State who "carried out the operation in response to calls for targeting citizens of the coalition" of countries fighting IS in Syria and Iraq.

Speaking Thursday morning, U.K. Defense Secretary Michael Fallon said that Parliament is currently reviewing its already stringent security measures.

Police forensics team examine a car in Parliament Square on March 22, 2017 in London, England.
Ray Tang | Anadolu Agency | Getty Images

Wednesday's attack unfolded around 2:40 p.m. local time when Masood drove a gray Hyundai SUV along a sidewalk on Westminster Bridge, before running to Parliament. There he was confronted by police, including unarmed PC Keith Palmer, who later died from stab wounds.

Tobias Ellwood, a member of Parliament who was at the scene at the time, was praised for his efforts to provide mouth-to-mouth resuscitation to Palmer.

London will continue as normal, never giving into terror: UK PM May
London will continue as normal, never giving into terror: UK PM May

The attack is the worst London has seen since July 7, 2005, when the capital was hit by a series of suicide bomb attacks on public transport during rush hour.

The city has been on "severe" alert since 2014, which indicates that an attack is "highly likely," in response to conflicts in Iraq and Syria. This was an increase from a previous level of "substantial," which implies a strong possibility of an attack.

Wednesday marked the first anniversary of suicide attacks in Brussels. Memorial services were held around the country to remember the 32 people killed and 320 injured by those attacks.

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Correction: This story was revised to correct the spelling of Mormon.