Police make arrests after assailant kills 3, injures dozens in attack outside British Parliament

, and Contact Reporter

A lone assailant struck at the heart of London on Wednesday, mowing down pedestrians with a car and then fatally stabbing a police officer outside Britain’s Houses of Parliament in an apparent terrorist attack that took place on the anniversary of twin bombings in Brussels.

Four people were reported dead in the attack, including the police officer and the assailant, and dozens were injured. Tobias Ellwood, the Foreign and Commonwealth Office minister, had administered CPR to the officer as he lay on the sidewalk, but it was ultimately not enough.

» UPDATE: Suspect in London attack was previously investigated by MI5

Prime Minister Theresa May was at Parliament at the time and was rushed away in the back of a silver Jaguar. Speaking to journalists later outside her residence at 10 Downing St., May condemned what she described as “a sick and depraved terrorist attack.”

“The location of this attack was no accident,” she said. “These streets of Westminster — home to the world’s oldest Parliament — are engrained with a spirit of freedom that echoes in some of the furthest corners of the globe. And the values our Parliament represents — democracy, freedom, human rights, the rule of law — command the admiration and respect of free people everywhere.”

May pledged that lawmakers would meet Thursday and Londoners would go about their day as usual, “never giving in to terror and never allowing the voices of hate and evil to drive us apart."

Mark Rowley, acting deputy commissioner at London's Metropolitan Police, told reporters Wednesday that it appeared there was only one attacker, “but it would be foolish to be overconfident early on.”

Rowley declined to identify the attacker but said authorities believe they know who he was, and the working assumption is that he was inspired by “Islamist-related terrorism.”

Police raided six addresses overnight, resulting in eight arrests.

On Thursday, Rowley revised the death toll from five to four: the attacker, the police officer and two civilians. At total of 29 people required hospitalization, he said, and seven of them were in critical condition.

Authorities were still working out the number of "walking wounded." Police had previously given the number of injured as around 40.