The bodies were discovered on Wednesday morning. A police doctor attended the scene.
The 49-year-old man and his 41-year-old wife were already dead. The 13-year-old daughter was taken to hospital but died of her injuries.
The police officer worked with federal traffic police. An investigation is underway to establish whether he was allowed to take his weapon home. Normally this is not permitted though there are exemptions e.g. in case of a general terrorist threat. Individual officers can receive permission to take their weapon home, but only after an extensive procedure.
Help in connection with thoughts of suicide is available via the tollfree number 1813 or via 106.