INDIANTOWN, Fla. – A Florida man stormed into a house and fatally shot his ex-girlfriend as her 10-year-old daughter took an online class, with the girl's teacher and other students hearing part of the commotion before the slaying, authorities said.The school year's first day of instruction had just begun when a Warfield Elementary School teacher heard some kind of domestic disturbance from the girl's video chat Tuesday morning, Martin County Sheriff William Snyder said during a news conference.The teacher muted the girl's audio but then saw the girl cover her ears before the screen went blank; investigators later said the computer had been struck by a bullet.