PARIS (AP) — Prosecutors say a homicide investigation has been opened after a security guard at the Qatari Embassy in Paris was killed and a suspect arrested. The circumstances of the killing, including the method used, were not immediately clear. The prosecutor’s office said that “the use of a weapon is not at this time confirmed.” Some French press reports said the guard was killed around 7 a.m. outside the embassy in Paris’ posh 8th district, apparently beaten to death. Several French media reported that the suspect appeared to be mentally unstable. Police refused to comment on the killing.