FT. MYERS, Fla. -- A school resource officer is being accused of excessive force after using a taser on an autistic student. Now, that boy's mother says a misunderstanding has left her child confused and bruised.

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Dennis Caliguri, 15, has bruises to show for what happened when he encountered a school resource officer and his taser. Investigators said Dennis was so violent and out of control that it took five faculty members to restrain him and the taser was used to calm him down.

Dennis is autistic and functions at the level of a six-year-old. But at 5'8" tall and 220 pounds, his mother, Susan Caliguri, said he is big but harmless. So she was shocked to get a call from Cypress Lake High School saying he was acting out. When she got to the school, she was horrified.

"It was a nightmare. They had him handcuffed, his legs were tied, he was on the ground. They had four sheriffs on top of him. I mean, he is bruised down his back, they were stunning him and he was already down. He couldn't do anything," she said.

Susan calls it excessive force, but the Lee County Sheriff's Office said the taser was the only way to calm him down.

"The matter is that the deputy, if he is that tired out and he has a fear of being overpowered, his weapon being taken away from him, he has to be able to overpower and be able to take control of the situation," said Charles Ferrante, Lee County Sheriff's Office

School administrators said Dennis got upset after being told not to come to school one day last week. He misunderstood and thought he was in trouble and started throwing papers.

Despite his mother's concerns, Dennis was arrested and charged with disturbing the peace and resisting arrest.