HELSINKI (AP) — Swedish police have arrested a second person in the April 7 truck attack that killed four people and injured 15 others in Stockholm.

Police spokesman Simon Bynert said Monday the male suspect was arrested Sunday, but he did not elaborate.

Rakhmat Akilov, a 39-year-old Uzbek man, has pleaded guilty to a terrorist crime after ramming the truck into a crowd outside a main pedestrian shopping street in the Swedish capital. Police have not disclosed a motive for the attack and no extremist group has claimed responsibility for it.

Akilov's Swedish residency application was rejected last year but police said there was nothing to indicate he might plan an attack.

This version corrects the name of the police spokesman to Bynert.