Aarau cantonal police confirmed the arrest early Monday, stating that the investigation into the exact sequence of events, background, and possible motive is ongoing. "At this time, it is assumed that the perpetrator acted alone," police said in a statement.
The shooting occurred at around 2:30 a.m. local time on Sunday at the Schachen race track, where a techno rave was being held. Organizers had expected 3,500 attendees. Spinelli died at the scene, while four men and a woman, aged between 24 and 27, were hospitalized with injuries ranging from minor to severe. An eyewitness told Swiss outlet Blick that he heard gunshots minutes after the music stopped and initially mistook them for fireworks; a woman who told him to hide was later shot.
On Sunday afternoon, police spokesperson Michael Leupold acknowledged officers had no leads on the perpetrator and were unsure whether it was one person or multiple. The manhunt involved cooperation with German police from Freiburg, given Aarau is less than 40 km from the German border.
Italian Prime Minister Giorgia Meloni expressed confidence that Swiss authorities would "shed full light on what happened and find anyone responsible." Italy's foreign ministry said it was sending officials to Zurich to closely follow the investigation and confirmed that two other Italians were slightly injured and have returned home.