Swiss police said on September 2 that the man suspected of shooting and killing an Italian woman at a rave party in Aarau was a "lone wolf" attacker.
Aargau cantonal police commander Michael Leupold told a press conference on Wednesday that there were no signs anyone else was involved in the attack, which happened in the early hours of Sunday and left a 22-year-old Italian woman dead and five others injured.
"We therefore strongly believe that the shooting was the act of a single individual," Leupold said.
The suspect, a 43-year-old Swiss man, turned himself in on Monday at a police station in Delemont in the northwestern canton of Jura. According to prosecutors, he has remained silent while in custody.
Leupold said the motive for the attack was still unknown and that the suspect had no prior criminal record.
Aargau cantonal prosecutor Christoph Ruedi said the suspect is believed to have "psychological issues" and has stayed silent since his arrest.
The incident shocked Switzerland, where shootings, especially those involving multiple victims, are rare even though gun ownership is relatively common.
Authorities said they found two pistols and an AK-47 rifle in the suspect's car.
Meanwhile, the rave organizers said they were "shocked and saddened," writing on their website that they "will do everything in their power to support the police in their work."
"A rave should always be a place of joy and love. Never a place where people are killed, injured, or left in fear."
