Police have identified the first suspect of two arrested so far in Thursday's van attack in Barcelona, Spain, that killed at least 13 and wounded dozens more.

Driss Oukabir, 28, was reportedly apprehended Thursday evening by police, who say the Moroccan citizen was in the country legally.

Police said Oukabir rented the van that plowed into civilians in Barcelona's city center on the "Las Ramblas," popular with tourists.

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Barcelona authorities announced on Twitter that they are "treating him as a terrorist."

"There is no one holed up in any bar in the center of Barcelona. We arrested a man and are treating him as a terrorist attacker." https://t.co/5uEnP69ETI — Alexander Smith (@AlexSmithNBC) August 17, 2017

It is not clear if Oukabir was driving the car or was at the scene of the attack.

Authorities have also not yet linked the suspect with any terrorist groups. The Islamic State in Iraq and Syria (ISIS), though, claimed responsibility for the attack on Twitter.

U.S. officials including President Trump were quick to condemn the attack. Trump said the U.S. "will do whatever is necessary to help."

This story was updated at 4:21 p.m.