The man police believe is responsible for Wednesday's terrorist attack at London's Westminster Bridge has been identified as U.K. native Khalid Masood.
Police said Masood, 52, was known to authorities and has a range of previous convictions for assaults, including grievous bodily harm, possession of offensive weapons and public order offenses. His most recent conviction was in December 2003 for possession of a knife, according to the Metropolitan Police Service in London.
Massod was born in Kent in southeast England and detectives believe he was most recently residing in the West Midlands in western-central England. He was also known by a number of aliases, according to police.
Masoon has not been convicted of any terrorism offenses, police noted.
Police said Masoon was not the subject of any current investigations and there was no prior intelligence regarding his intent to launch a terrorist attack.
8 arrested over 'sick' terror attack in London that killed 4, including attacker
Earlier today, U.K. Prime Minister Theresa May addressed members of Parliament, speaking solemnly about the "act of terrorism that tried to silence our democracy."
"But today we meet as normal -- as generations have done before us, and as future generations will continue to do -- to deliver a simple message: We are not afraid," she said at Britain's House of Commons. "And our resolve will never waiver in the face of terrorism."
May discussed what intelligence and security officials had so far gleaned about the attack, noting that the assailant was born in the United Kingdom and had been on the radar of security services.
Matt Dunham/AP PhotoPolice secure the area on the south side of Westminster Bridge close to the Houses of Parliament in London, March 22, 2017.more +
Three people, including a police officer, were killed and at least 29 others were injured in Wednesday's attack, which authorities have declared a terrorist incident. A man believed to be the attacker was shot dead by police at the scene, according to the Metropolitan Police Service.
Police have said they believe the attack was "inspired by international terrorism" and they are looking at the suspect's possible associates.
In a statement published today by its media outlet, Amaq News Agency, ISIS called the attacker "a soldier of the Islamic State" and said he "carried out the operation in response to calls to target citizens of the international coalition."
Stefan Rousseau/PA via APA policeman points a gun at a man on the ground as emergency services attend the scene outside the Palace of Westminster, London, March 22, 2017.more +
During a press conference this morning, Metropolitan Police acting deputy commissioner Mark Rowley said eight people were arrested in connection with Wednesday's attack after overnight raids at six locations, including in Birmingham and London.
The attack began around 2:40 p.m. local time Wednesday, when a car struck pedestrians and three police officers on Westminster Bridge. The car then crashed into the fence around the Houses of Parliament, and a man armed with a knife attacked an officer who was standing guard. The suspect, who authorities believe acted alone, was then shot and killed by police, according to the Metropolitan Police Service.
In an initial news conference Wednesday night, Rowley said the suspect tried to enter Parliament but was stopped "very close to the gate."
APTNEmergency services workers respond to the scene of an incident near Westminster Bridge and the Houses of Parliament in London on March 22, 2017.more +
The officer who died, identified as 48-year-old Keith Palmer, was not armed. Palmer, a husband and father, had served for 15 years with the Metropolitan Police Service, Rowley added.
The attack, which occurred on the one-year anniversary of attacks in Brussels that killed 32 people and wounded hundreds, was reminiscent of vehicle attacks last year in both Berlin and Nice, France.
Metropolitan Police/AFP/Getty ImagesAn undated handout picture released by the British Metropolitan Police shows PC Keith Palmer who was killed during the terror incident at the Houses of Parliament in London on March 22, 2017.more +
A spokesperson for Enterprise Rent-A-Car, an American car rental company headquartered in Missouri, confirmed to ABC News that the vehicle used in Wednesday's attack in London was rented from one of its branches in Birmingham, England. The spokesperson refused to provide additional details about the individual who rented the car, when it was rented and how it was paid for.
"We can confirm that the car used in the tragic attack in London yesterday afternoon was one of ours. An employee identified the vehicle after seeing the license plate in an image online. We ran another check to verify, and immediately contacted the authorities," the spokesperson in a statement today. "We are cooperating fully with the authorities and will provide any assistance that we can to the investigation."
Toby Melville/ReutersInjured people are assisted after an incident on Westminster Bridge in London, March 22, 2017.
Eyewitnesses described to ABC News what they saw as the attack unfolded. One witness, Richard Tice, said he saw injured people lying on the pavement on Westminster Bridge. The car involved in the attack appeared to have jumped the curb, knocking people over, he added.
Bradford and Joanne Buck, a U.S. couple visiting London from Connecticut, had just emerged from the city's subway system when they saw the crashed car.
"We saw all of this commotion going on. Looked over, there was a car crashed into the gate, door opened and there was a man down right next to the car, all curled up," Bradford Buck said in an interview this morning on "Good Morning America."
"The next thing I saw was a few police officers with machine guns," he added. "Very, very hectic. This must have just happened when we came up from the Underground."
Toby Melville/ReutersA woman assists an injured person after an incident on Westminster Bridge in London, March 22, 2017.
The couple said they were in shock at first but immediately took cover. After a few minutes, they felt safe enough to leave the area.
"Just couldn't believe it was happening," Joanne Buck told "GMA" this morning. "Just saw the machine guns and knew we had to take cover quickly.”
Despite heavy police presence, the couple said Londoners appeared to be doing well after the attack.
"The people are great; they're going about their business. There's a lot of police officers with machine guns walking around, which we hadn't seen before this happened. But the mood of the people is great," Bradford Buck told "GMA."
He added, "We're going to carry on with our vacation. We're not going to let it stop us and hope to finish our sightseeing while we are here in London."