A police officer who was among those killed in Wednesday’s terror attack outside the British Parliament building in London has been identified as 48-year-old Keith Palmer, who worked for the Metropolitan Diplomatic Protection Group. He was a father and a husband.

The attack left four other people dead, including the attacker, and more than 40 injured. The assailant, who has not been identified, appeared to run over bystanders with a vehicle, then stabbed Palmer before he was shot to death by another officer trying to enter the Parliament building.

Metropolitan Police Department Officer Keith Palmer, 48, was fatally stabbed in a terrorist attack Wednesday.

James Cleverly, who serves as the member of Parliament for the county of Braintree, called the slain officer a “lovely man, a friend.”

I've known Keith for 25 years. We served together in the Royal Artillery before he became a copper. A lovely man, a friend. I'm heartbroken. https://t.co/LgF4rQ7Vmg — James Cleverly MP (@JamesCleverly) March 22, 2017

Palmer, a 15-year police veteran, was not armed when he was fatally stabbed.

A/Dep Cmsr Rowley: "The suspected attacker was shot dead by an armed officer - meaning five people in total have died" — Metropolitan Police (@metpoliceuk) March 22, 2017

In a statement posted to Facebook, London Mayor Sadiq Khan said that Palmer was “protecting our city and our democracy from those who want to destroy our way of life.”

“Today is an incredibly sad and somber day, especially for the Metropolitan police service,” Mark Rowley, Metropolitan Police assistant commissioner, said at a press conference Wednesday night. “It is only right that I finish by mentioning the pride I feel in the swift and brave response from our officers, especially from those who ― without fear for their own safety ― confronted the terrorist.”

An air ambulance landed on the grass outside the Palace of Westminster as medical crews rushed in to treat the injured.

Air ambulance just landed at Parliament Square, Westminster, dozens of police cars pic.twitter.com/TZVTO6IzDR — Peter Yeung (@ptr_yeung) March 22, 2017

Among those hurt were three French students aged 15 and 16, Le Telegramme reported. The publication said the teens were walking on Westminster Bridge when they were struck by a vehicle.

Rowley said three officers returning from a commendation ceremony also were struck by the vehicle and were in serious condition. A doctor at St. Thomas Hospital described the victims’ injuries as “catastrophic,” according to the Press Association.

A Reuters photographer captured the chilling scene, which showed injured and bloodied victims lying on the ground. In one photo, a body could be seen stuck under the wheel of a bus. Two of those who were killed were struck on the bridge.

Tobias Ellwood, a member of Parliament and British foreign minister for the Middle East and Africa, rushed to the aid of Palmer after he was stabbed. Ellwood, a former soldier, attempted CPR on the officer and tried to stop the bleeding by applying pressure to his wound. Ellwood stayed with Palmer until medical crews arrived.

Stefan Rousseau/PA Images via Getty Images NOTE ALTERNATE CROP Conservative MP Tobias Ellwood stands amongst the emergency services at the scene outside the Palace of Westminster, London, after policeman has been stabbed and his apparent attacker shot by officers in a major security incident at the Houses of Parliament. (Photo by Stefan Rousseau/PA Images via Getty Images)Embed Url Embed Asset Code Enter asset code

Scotland Yard lowered its flag to half-staff following the attack.

Flag at half-mast over Scotland Yard tonight to mark the death of our officer & the other victims of this afternoon’s attack in #Westminster pic.twitter.com/NqaGSqJtmt — Metropolitan Police (@metpoliceuk) March 22, 2017

The attack came exactly one year after a terrorist attack in Brussels left more than 30 people dead.