Photo gallery: Attack in London

An undated handout photo made available by the London Metropolitan Police (MPS) showing Kurt Cochran (L) and his wife Melissa. Kurt Cochran was killed in what authorities believe was a terror attack on March 22 in London, leaving five people dead, including the attacker, and 31 people injured.

Floral tributes left in honour of the victims of the London terror attack are pictured in Parliament Square in London on March 25, 2017.

Plastic candles lie along Westminster Bridge in London on March 24, 2017. Well-wishers have flocked to the scene of the March 22 attack to pay their respects to those killed.

People place flowers outside Britain’s parliament in London on March 25, 2017 for the victims of the Westminster attack.

Floral tributes left in honour of the victims of the London terror attack are pictured in Parliament Square London on March 25, 2017.

Floral tributes left in honour of the victims of the London terror attack are pictured in Parliament Square in London on March 25, 2017.

A man lays flowers outside New Scotland Yard in central London, Britain on March 23, 2017.

A picture of British policeman Keith Palmer is seen among flowers near the Houses of Parliament following the March 22 attack in central London.

A police officer lays a bunch of flowers in honour of the victims of the March 22 terror attack at the end of Westminster Bridge by the Houses of Parliament in central London on March 23, 2017 after the bridge reopened.

Police forensic teams gather outside the Houses of Parliament in London on March 23, 2017.

Newly appointed London Metropolitan Police Commissioner Cressida Dick, at right, bows her head during a minute of silence for their fallen officer, PC Keith Palmer, outside New Scotland Yard in London on March 23, 2017.

A woman prays near flowers left close to the Houses of Parliament in London on March 23, 2017.

Emergency personnel work following an attack in London on March 22, 2017.

A forensic tent is seen near St Thomas’ Hospital close to the Palace of Westminster in London on March 22, 2017, following a terror attack.

British Prime Minister Theresa May gives a statement outside 10 Downing Street in London on March 22, 2017, following a terror attack in the Westminster area of the city earlier Wednesday.

British police officers guard the entrance The Mall as the roads leading to Parliament Square in central London remain cordoned off in the aftermath of a terror incident at the Houses of Parliament on March 22, 2017.

Reporters and police are stationed outside Westminster Abbey next to the Houses of Parliament on March 22, 2017, in London following a terror attack earlier that day.

A British police officer stands guard at a cordoned off road leading toward Parliament Square in London on March 22, 2017, in the aftermath of a terror incident.

An armed police officer stands guard near Westminster Bridge and the Houses of Parliament on March 22, 2017, in London.

A forensic expert works following an attack on Westminster Bridge in London on March 22, 2017.

Emergency service vehicles are pictured on Westminster Bridge, adjacent to the Houses of Parliament in Westminster in London on March 22, 2017.

An attack suspect is treated by emergency services outside the Houses of Parliament in London on March 22, 2017.

A wounded person is treated by emergency services near Westminster Bridge and the Houses of Parliament on March 22, 2017, in London.

A wounded member of the public is treated by emergency services near Westminster Bridge and the Houses of Parliament on March 22, 2017, in London.

Armed police take cover outside the the Houses of Parliament in London on March 22, 2017.

An armed British police officer stands on duty as members of emergency services gather at the Carriage Gates entrance of the Houses of Parliament in Westminster, London, on March 22, 2017.

Armed police officers gather outside the Houses of Parliament in London on March 22, 2017, after the House of Commons sitting was suspended as witnesses reported sounds like gunfire outside.

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.

Armed police respond after major incidents outside the Houses of Parliament in central London on March 22, 2017.

Conservative MP Tobias Ellwood, center, stands among emergency responders at the scene outside the Palace of Westminster in London on March 22, 2017.

Emergency responders provide medical attention close to the Houses of Parliament in London on March 22, 2017.

A member of the public is treated by emergency responders near Westminster Bridge and the Houses of Parliament on March 22, 2017, in London.

An armed police officer stands on Parliament Square outside the Houses of Parliament in London on March 22, 2017, after the House of Commons sitting was suspended as witnesses reported sounds like gunfire outside.

Police secure the area on the south side of Westminster Bridge close to the Houses of Parliament in London on March 22, 2017.

Armed police officers enter the Houses of Parliament in London on March 22, 2017, after the House of Commons sitting was suspended as witnesses reported sounds like gunfire outside.

Emergency personnel tend to an injured person close to the Palace of Westminster in London, on March 22, 2017.