(AP) — Florida investigators say they may never know why a Marine veteran killed a Lakeland family of four he had no connection with. Authorities say Bryan Riley confessed to killing a 40-year-old man, his 33-year-old girlfriend, their 3-month-old son and the woman’s 62-year-old mother. An 11-year-old girl was critically wounded. Polk County sheriff’s investigators say the 33-year-old suspect told them “You know why I did this.” But prosecutor Brian Haas said the only explanation so far is mental illness. Riley’s girlfriend told investigators that he had been saying for a week that he was talking directly to God.