Update: Khalid Masood, 52, has been named as the attacker. He has a criminal record for violence.
British media outlets have been publishing pictures of the suspect with blur bubbles to obfuscate his race/ethnicity. The German media outlet BILD appears to have been the first to publish a non-blurred photo.
The style of attack is similar to other jihadist attacks using vehicles in France, Germany, and Ohio. The perp rammed a crowd of people with his car. Then he got out of the car armed with a knife. A police officer shot him in the chest.
ISIS has published articles urging this style of attack. It is part of a strategy they call “death by one thousand cuts.” Jihadists know that it has become harder to perform sophisticated attacks, like airplane hijackings. So they urge small attacks, using household items.