UPDATE 7:12 P.M. EST: Unfortunately, police are now reporting a fifth person has died as a result of their wounds.
Authorities have also now officially released the name of the hero policeman who died protecting Parliament: Keith Palmer, a husband and father who'd been an officer for 15 years.
PM May thanked the "exceptional men and women" of the police force; she added:
"The location of this attack was no accident. The terrorist 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."
The number of injured has also risen; police now say over 40 in all.
One year to the day after the deadly suicide bombings in Brussels, another act of terrorism has taken innocent lives.
Four are confirmed dead after a man drove a large vehicle into pedestrian traffic on Westminster Bridge in London. Two were killed by the vehicle; at least 20 others were injured, including three young students who were visiting from France.
After crashing into the railing, the driver, armed with a knife, abandoned the vehicle and tried to get into Westminster Abbey — where the U.K. Parliament convenes.
A police officer blocked his way and was stabbed; he later died of his wounds.
The assailant was reportedly then shot by police before he could make it into the building. Lawmakers inside Westminster were put on lockdown for over two hours as a precautionary measure.
Assistant Commissioner Mark Rowley of the National Counter-Intelligence Service addressed reporters with a full rundown of the tragic events: