Five people were killed and 40 others injured after an attacker plowed a car into a crowd of people on Westminster Bridge in London on Wednesday afternoon in what U.K. officials are investigating as an act of terrorism.

What we know so far:

The attack began around 2:30 p.m. local time, when the car struck pedestrians on the bridge before crashing into a gate outside the Houses of Parliament.

The knife-wielding suspect driving the car was shot after stabbing a police officer guarding the building.

Both the officer and assailant died at the scene, officials said.

Some of the 40 wounded on the bridge are said to have suffered “catastrophic” injuries.

Parliament was placed on lockdown for several hours.

British police are treating the incident as terrorism.

Officials said they believe the attack was carried out by a lone individual.

The suspect has yet to be publicly identified.

A full counterterrorism investigation is under way.

London Mayor Sadiq Khan released a video statement condemning the attack.

“Londoners will never be cowed by terrorism,” Khan said.

See a recap of the attack and its aftermath in the live blog below, and tune in Thursday morning for more live updates from London.