A Sarasota Sheriff's deputy was fired after he aggressively threw a special-needs student onto a school bus seat and threatened to shock her with a Taser during a videotaped confrontation on the bus.The deputy, Mark Perrin, was fired Wednesday after an internal investigation spurred by a videotape that shows him snatching a 17-year-old girl from her seat and flinging her across an aisle while others on the bus looked on in shock. Perrin also used profanity during the episode, authorities said.The situation began when an aide on the bus called 911 to say that the student threw a plastic bottle, punched her in the stomach and kicked her wrist.The bus, from Sarasota High School, pulled over at Cattlemen Road and Cattleridge Boulevard about 3 p.m. on Dec. 15.Authorities say that Sarasota County firefighters were the first to arrive, and that the aide and driver remained on the bus as the girl refused to get out of her seat.When Perrin shows up, he sees the teenager in her seat a few rows back. He asks, "What's your problem, girl?"The teenager, who has not been named in reports, is told to stand up, but refuses."I'll snatch your ass out of that seat," the deputy says.He then grabs the teenager by her sweatshirt and violently throws her across the aisle and face down into another seat. The deputy climbs on top of the teenager's back and struggles to restrain her."Put both hands behind your back before I Tase you," he says.The girl can be heard screaming while others on the bus back away. She later told internal affairs investigators that she could hear her sweat shirt ripping and that she was surprised the deputy grabbed her out of the seat.