Four people were killed, including a police officer, and at least 40 other people were injured in an attack in London that authorities have declared a terrorist incident. A man believed to be the attacker was also killed, shot by police at the scene.
The attack began when a driver struck pedestrians and three police officers on Westminster Bridge, London's Metropolitan Police said.
Witness Richard Tice told ABC News that he saw injured people on the pavement. According to him, the car jumped the curb, knocking over pedestrians.
The car then crashed into the fence around the Houses of Parliament, and a man armed with a knife attacked an officer who was guarding Parliament, police said.
The suspect, who authorities believe acted alone, was shot and killed by police. In a press conference Wednesday evening, Metropolitan Police acting Deputy Commissioner Mark Rowley said the suspect tried to enter Parliament but was stopped "very close to the gate."
The officer who died, identified as 48-year-old Keith Palmer, was not armed, he added. Palmer, a husband and father, served for 15 years with the Metropolitan Police, Rowley said.
Police believe that the attack was "inspired by international terrorism" and that they know the attacker's identity, but Rowley did not give further details. Authorities are also looking at the suspect's possible associates.
As police swarmed the area, Tom Peck, a British journalist, told ABC News from his office in London that he heard a bang, lots of screaming and then several gunshots.
Authorities said they received different reports today of a person in the River Thames, a car that collided with pedestrians and a man armed with a knife.
A seriously injured woman was pulled from the Thames and was receiving medical treatment, an official with the Port of London Authority told ABC News.
Three French high school students were also among the injured, according to French officials.
Tobias Ellwood, a member of Parliament, was seen giving first aid to a victim.
Rowley said earlier in the day, "This is a day we plan for but hope it will never happen. Sadly, it is now a reality."
"We will continue to do all we can to protect the people of London," he added.
The Parliament building had been on lockdown after the attack, and hundreds of people have since left.
The House of Commons and the House of Lords will resume normal operations on Thursday.
"Business must return to normal as quickly as possible," Rowley said Wednesday evening.
U.K. Prime Minister Theresa May described the attack as "appalling" and "sick and depraved" in a press conference Wednesday evening.
She said the location chosen for the attack was "no accident" and that Britain's threat level will remain at severe, where it has been for some time.
"The terrorists chose to strike at the heart of our capital city, where people of all nationalities, religions and cultures come together to celebrate the values of liberty, democracy and freedom of speech," she said.