An injured person is assisted after an incident on Westminster Bridge in London, Britain March 22, 2017. REUTERS/Toby Melville
Police officers work at the scene after an attack on Westminster Bridge in London, Britain, March 22, 2017. REUTERS/Hannah McKay
Flowers are laid at the scene after an attack on Westminster Bridge in London, Britain, March 22, 2017. REUTERS/Hannah McKay
A forensics investigator works at the scene after an attack on Westminster Bridge in London, Britain March 22, 2017. REUTERS/Hannah McKay
Injured people are assisted after an incident on Westminster Bridge in London, March 22, 2017. REUTERS/Toby Melville
A fire officer works at the scene after an attack on Westminster Bridge in London, Britain, March 22, 2017. REUTERS/Hannah McKay
Injured people are assisted after an incident on Westminster Bridge in London. REUTERS/Toby Melville
A forensic investigator works at the scene after an attack on Westminster Bridge in London, Britain, March 22, 2017. REUTERS/Hannah McKay
Armed police respond outside Parliament during an incident on Westminster Bridge in London. REUTERS/Stefan Wermuth
A woman ducks under a police tape after an incident on Westminster Bridge in London. REUTERS/Toby Melville
A man lies injured after a shooting incident on Westminster Bridge in London, March 22, 2017. REUTERS/Toby Melville
Police officers work at the scene after an attack on Westminster Bridge in London, Britain, March 22, 2017. REUTERS/Hannah McKay
Police officers work at the scene after an attack on Westminster Bridge in London, Britain, March 22, 2017. REUTERS/Hannah McKay
An air ambulance lands in Parliament Square during an incident on Westminster Bridge in London. REUTERS/Stefan Wermuth
A woman assists an injured person after an incident on Westminster Bridge in London, March 22, 2017. REUTERS/Toby Melville
Police officers work at the scene after an attack on Westminster Bridge in London, Britain, March 22, 2017. REUTERS/Hannah McKay
Forensics investigators work at the scene after an attack on Westminster Bridge in London, Britain March 22, 2017. REUTERS/Hannah McKay
UK Parliament, Westminster Bridge terror attacks kill five in London