German media on Saturday reported that the Berlin truck attacker who killed 12 people last month may have gotten his gun in Switzerland. ZDF reported that Anis Amri’s phone data showed he had made several trips to Switzerland prior to the attack, raising questions about whether the gun he used for the attack may have been obtained in Switzerland. Switzerland’s Office of the Attorney General said Wednesday it had opened criminal proceedings into Amri, but it did not say whether he had stayed in the country or gotten his weapon there. The proceedings are meant to “clarify possible points of contact with Switzerland,” a spokesperson for the office told Reuters. Twelve people were killed last month in the attack, when Amri allegedly plowed a hijacked truck into a crowded Christmas market. Investigators are now trying to determine how Amri was able to evade authorities prior to the attack.