Metropolitan Nashville Police Department/ReutersThe suspected shooter who killed three children and three adults at a school in Nashville on Monday morning sent a series of dark messages to a friend in the minutes leading up to the attack, according to a report.Police identified Audrey Hale, 28, as the person responsible for the bloodshed at the Covenant School. In a statement, authorities said the first 911 call about shots being fired at the private Christian school was made at 10:13 a.m.Just