Thirteen people were killed and dozens more injured when a van drove onto the sidewalk and down a pedestrian zone in a popular tourist area of Barcelona, Spain, Thursday.
One person has been arrested, police tweeted.
The incident happened in the city's historic Las Ramblas district. It's a popular street that has a pedestrian path down the middle. It's lined with shops, and is a very popular place for tourists.
Vehicles have been used more often in extremist attacks in Europe over the past year, The Associated Press notes. The most deadly attack happened in July 2016 when a tractor-trailer crashed into people celebrating Bastille Day in Nice, France, killing 86 people.
The U.S. responds
President Donald Trump tweeted about the attack, saying the U.S. will do whatever it can to help.
The U.S. Department of Homeland Security also released a statement on the attack, saying, in part: "We will not let terrorism become the new normal. Instead, such acts of violence only harden our resolve to fight back against violent extremists, bring them to justice, and dismantle their networks."