Swiss police have confirmed they arrested a 43-year-old suspect in relation to a deadly shooting incident at a rave in Aarau.A 22-year-old Italian woman was killed and five people injured after the shooting at the event at a covered horse race track in the early hours of Sunday morning in Switzerland.Police launched a massive operation and just before 1am on Monday arrested a 43-year-old Swiss man on suspicion of carrying out the attack, it said."Investigations into the exact circumstances of the incident, as well as its background and possible motive, are currently underway. At this stage, it is assumed that a single perpetrator was involved," police in the canton of Aargau said in a statement.Police on Sunday said they were investigating three possible motives for the shooting, including a mass shooting, an act of terrorism or an unknown criminal motive.Cartridges found at the crime scene indicated two calibres of bullets, possibly from a pistol and a second, larger weapon, potentially an assault rifle, police said.Police officers stand guard near the site of a rave party, following a deadly shooting incident at an event on Sunday, near the Schachen horse racing track, in Aarau (Reuters)Four men and one woman, aged between 24 and 27 years old, were taken to the hospital with injuries ranging from minor to severe.All of the victims are residents of Switzerland, police said. They did not release their names in line with Swiss privacy rules.The shots were fired on the sidelines of the "Aarauer Rave," an annual techno party that drew around 3,500 people to the Schachen racecourse between 3pm on Saturday and 2am on Sunday, according to Blick.A reader told the newspaper they had heard "repeated shots," and a video obtained by the newspaper captured the sound of multiple gunshots at 2.35am. Another witness who was present said they initially thought the noise was fireworks, before hiding under the DJ booth.Swiss DJ Tekibo, who was performing at the rave, wrote on Instagram that “what happened at Aarauer rave is absolutely heartbreaking.”“Techno and raves are supposed to be a place for freedom and safety, never a place where something like this happens,” he added.Switzerland has one of the highest rates of civilian gun ownership in Europe, with around 27 firearms for every 100 residents, behind only a small group of countries such as Finland, Austria and Norway. Despite this, violent shootings remain rare.More follows on this breaking news story...Subscribe here to get the latest updates from The Independent