A Long Island school bus attendant pleaded not guilty Thursday to charges that he assaulted a 5-year-old autistic boy as he rode the bus home on Monday.

Richard Mason, of Brentwood, New York, allegedly grabbed Connor Shirangi's arm and pinned it behind the child's back in an attempt to discipline him, police told CBS news.

Shirangi, a special needs student in the Commack school district in Suffolk County, New York, sustained a fractured arm and bruises to his face and abdomen, a New York CBS affiliate reported.

“Excessive force was used and my child was severely injured,” the boy’s mother, Desiree Johnston-Shirangi, told CBS. “Aside from the broken arm he has bruising about the waist consistent with being tied down.”

Shirangi-Johnston told the news organization that her son was apparently swinging his feet and kicking the seat of the bus when Mason “got upset and handled him the way you wouldn’t handle anybody.”

“My son was going through this and the fear that he had to the point that he urinated in his pants and I wasn’t there,” she told CBS.

Mason, an employee of the ACME Bus Corp. which contracts with the school district, said he was attempting to keep the boy from harm. "He was pounding his hand against the window and to prevent the window from shattering, I blocked him," he told Channel 12 Long Island.

The bus company said in a statement that Mason was trying to stop a fight between two boys when Shirangi began hitting the window.

He has been suspended pending the investigation and trial, the Commack School District said in a statement.

“As soon as we learned of the allegations, we immediately confirmed that the defendant had been removed from any and all District routes and will have no contact with our students,” they said in the statement. “ACME has assured the District that the driver assistant had been properly screened and trained and that he had no prior incidents.”

Mason was released after an arraignment hearing in a Suffolk County court Thursday. He pleaded not guilty to charges of third-degree assault and acting in a manner to injure a child.