Keith Palmer's 15-year career as a London police officer was brutally ended Wednesday by a terrorist's knife, reports CNN.

"He was someone who left for work today expecting to return home at the end of his shift, and he had every right to expect that would happen," Metropolitan Police Acting Deputy Commissioner Mark Rowley said in an evening press conference.

Palmer, a 48-year-old father, was one of three people killed in Britain's most lethal terror attack since the 2005 public transit bombings.

The assailant drove a car through crowds of people, injuring dozens before crashing into a fence near London's Houses of Parliament.

Witnesses said the attacker then got out of his car, brandishing the knife that he used to fatally stab Palmer.

A member of the parliamentary and diplomatic protection command, Palmer was not carrying a gun, said Rowley, Britain's most senior counterterror police officer.

Bystanders rushed to Palmer's aid as he lay bleeding on the cobblestone street, including Conservative Member of Parliament (MP) Tobias Ellwood. But there was nothing they could do.

"Keith Palmer was killed while bravely doing his duty, protecting our city and the heart of our democracy from those who want to destroy our way of life," London Mayor Sadiq Khan said.

"He personifies the brave men and women of our police and emergency services who work around the clock to keep us safe -- tonight all Londoners are grateful to them."