Swiss police said on Monday that they had arrested a 43-year-old suspect in relation to a deadly shooting at a rave in the town of Aarau at the weekend.
A 22-year-old Italian woman was killed and five people were injured in the early hours of Sunday morning at the event, held at a covered horse racing track.
Police launched a massive operation and just before 1:00 AM on Monday arrested a 43-year-old Swiss man on suspicion of carrying out the attack, they said.
"Investigations into the exact circumstances of the incident, as well as its background and possible motive, are currently under way.
At this stage, it is assumed that a single perpetrator was involved," police in the canton of Aargau said in a statement. They gave no further details.
Police on Sunday said they were investigating three possible motives including a mass killing, an act of terrorism or an unknown criminal motive.
Cartridges found at the scene indicated two calibres of bullet, possibly from a pistol and an assault rifle, police said.
The Swiss newspaper Tages-Anzeiger said cartridges found resembled those used in the Russian AK-74 assault rifle and its variants.
Police declined to comment on the report.
The 22-year-old Italian who died was named as Maria Spinelli by Italian Prime Minister Giorgia Meloni.
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