Police forces have cordoned off an area around the Houses of Parliament following a suspected terrorist attack in which 4 people, including a police officer, have died and at least 20 other people were injured on March 22, 2017 in London, England. (Photo by Wiktor Szymanowicz/Barcroft Images)





A member of the public is treated by emergency services near Westminster Bridge and the Houses of Parliament on March 22, 2017 in London, England. A police officer has been stabbed near to the British Parliament and the alleged assailant shot by armed police. Scotland Yard report they have been called to an incident on Westminster Bridge where several people have been injured by a car. (Photo by Carl Court/Getty Images)





A member of the public is treated by emergency services near Westminster Bridge and the Houses of Parliament on March 22, 2017 in London, England. (Photo by Carl Court/Getty Images)





A policeman points a gun at a man on the floor as emergency services attend the scene outside the Palace of Westminster, London, Wednesday, March 22, 2017. (Photo by Stefan Rousseau/PA Wire via AP Photo)





Police secure the area close to the Houses of Parliament in London, Wednesday, March 22, 2017. The leader of Britain's House of Commons says a man has been shot by police at Parliament. David Liddington also said there were “reports of further violent incidents in the vicinity”. London's police said officers had been called to a firearms incident on Westminster Bridge, near the parliament. Britain's MI5 says it is too early to say if the incident is terror-related. (Photo by Matt Dunham/AP Photo)





An armed police officer stands on Parliament Square outside of the Houses of Parliament in London, Wednesday, March 22, 2017 after the House of Commons sitting was suspended as witnesses reported sounds like gunfire outside. (Photo by Kirsty Wigglesworth/AP Photo)





Police secure the area on the south side of Westminster Bridge close to the Houses of Parliament in London, Wednesday, March 22, 2017. (Photo by Matt Dunham/AP Photo)





Emergency services staff provide medical attention close to the Houses of Parliament in London, Wednesday, March 22, 2017. (Photo by Matt Dunham/AP Photo)





Conservative MP Tobias Ellwood, left, stands amongst the emergency services at the scene outside the Palace of Westminster, London, Wednesday, March 22, 2017. (Photo by Stefan Rousseau/PA Wire via AP Photo)





Emergency services staff provide medical attention close to the Houses of Parliament in London, Wednesday, March 22, 2017. (Photo by Matt Dunham/AP Photo)





Emergency services transport an injured person to an ambulance, close to the Houses of Parliament in London, Wednesday, March 22, 2017. (Photo by Matt Dunham/AP Photo)





Emergency services at the scene outside the Palace of Westminster, London, Wednesday, March 22, 2017. (Photo by Stefan Rousseau/PA Wire via AP Photo)





A bloodied hand is emerges as a person is treated at the scene outside the Houses of Parliament London, Wednesday, March 22, 2017. London police say they are treating a gun and knife incident at Britain's Parliament “as a terrorist incident until we know otherwise”. The Metropolitan Police says in a statement that the incident is ongoing. It is urging people to stay away from the area. Officials say a man with a knife attacked a police officer at Parliament and was shot by officers. Nearby, witnesses say a vehicle struck several people on the Westminster Bridge. (Photo by Yui Mok/PA Wire via AP Photo)





Emergency personnel tend to an injured person close to the Palace of Westminster, London, Wednesday, March 22, 2017. (Photo by Yui Mok/PA Wire via AP Photo)





A woman lies injured after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





A man lies injured after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





A woman ducks under a police tape after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





A woman assists an injured person after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





An armed police officer assists a woman after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





An injured person lies on the ground after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





Injured people are assisted after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





A woman lies injured after an incident on Westminster Bridge in London on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





Armed police respond outside Parliament during an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





Injured people are assisted after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





An injured man is assisted on the footpath under Westminster Bridge after an incident in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





Injured people are assisted after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





An injured woman is assisted after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





An injured person is assisted after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





A woman assist an injured person after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





Armed police respond outside Parliament during an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Stefan Wermuth/Reuters)





Injured people are assisted after an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Toby Melville/Reuters)





A police officer gestures outside Parliament during an incident on Westminster Bridge in London on Wednesday, March 22, 2017. (Photo by Stefan Wermuth/Reuters)





An air ambulance lands in Parliament Square during an incident on Westminster Bridge in London, Britain on Wednesday, March 22, 2017. (Photo by Stefan Wermuth/Reuters)





Emergency services staff provide medical attention close to the Houses of Parliament in London, Wednesday, March 22, 2017. (Photo by Matt Dunham/AP Photo)





In this image taken from video emergency personnel gather around a body on the southside of Westminster Bridge that leads to the Houses of Parliament in London, Wednesday, March 22, 2017 after the House of Commons sitting was suspended as witnesses reported sounds like gunfire outside. The leader of Britain's House of Commons says a man has been shot by police at Parliament. David Liddington also said there were “reports of further violent incidents in the vicinity”. (Photo by ITN via AP Photo)





Armed police officers enter the Houses of Parliament in London, Wednesday, March 22, 2017 after the House of Commons sitting was suspended as witnesses reported sounds like gunfire outside. (Photo by Kirsty Wigglesworth/AP Photo)





London : Conservative Member of Parliament Tobias Ellwood, centre, helps emergency services attend to an injured person outside the Houses of Parliament, London, Wednesday, March 22, 2017. (Photo by AP Photo/PTI)





Police secure the area close to the Houses of Parliament in London, Wednesday, March 22, 2017. (Photo by Matt Dunham/AP Photo)





Conservative Member of Parliament Tobias Ellwood, centre, helps emergency services attend to an injured person outside the Houses of Parliament, London, Wednesday, March 22, 2017. (Photo by Stefan Rousseau/PA Wire via AP Photo)





A medic is seen near Westminster Bridge and the Houses of Parliament on March 22, 2017 in London, England. (Photo by Carl Court/Getty Images)