Video shows suspected London attacker barreling across Westminster Bridge

— -- Dramatic video of Wednesday's terrorist incident in London shows the suspected attacker barreling across Westminster Bridge in a car.

Surveillance video of the bridge broadcast by the BBC this evening shows the car weaving in and out of traffic as it crosses the bridge. At one point, something or someone can be seen falling into the River Thames below.

A seriously injured woman was later pulled from the river and received medical treatment, an official with the Port of London Authority told ABC News.

Four people were killed, including a police officer, and at least 40 other people were injured in the attack, near the Houses of Parliament. A man believed to be the attacker was also killed, shot by police at the scene. Authorities believe the suspect acted alone.

Authorities said they believe the attack was "inspired by international terrorism."

Britain's threat level remains at severe after the attack, said U.K. Prime Minister Theresa May.