KAAAWA, Oahu, Hawaii -- A Kaaawa Elementary School special education student has complained that bus drivers duct taped his mouth shut and beat him up last week.

One of the bus employees accused in the case has already left the employment of the bus contractor, KITV has learned.

Sherry Martinez was concerned when she picked her 11-year-old son up from Kaaawa Elementary School on Tuesday. He had sticky-tape on his face.

"And he says the bus driver had duct-taped his mouth shut because he wouldn't stop singing. And I was like, 'OK, this isn't OK," Martinez said.

So, she complained to the school and school officials asked for "disciplinary action" against the bus driver and aide who work for Kailua Local, the bus contractor that takes special education students to Kaaawa.

"I'm appalled. This is a special education bus with special education bus drivers and an aide. It's not like it's one individual. There's two different grown men, who must be in their forties and fifties," Martinez said.

On Thursday, she said the same two men did the same thing to her son and worse.

"And it wasn't a piece of duct tape over the mouth, it was duct tape all the way around his head," Martinez said.

She said as another student watched, the men assaulted him.

"They punched him -- close-fisted punched him -- pinched him, swore at him," Martinez said.

She said the Kailua Local employees also threw golf balls at him.

Martinez praised faculty and staff at Kaaawa Elementary School for quickly and aggressively investigating the incident.

Staff there said they took photos of welts and bruises on the boy's neck after the Thursday incident. School officials asked that one of the bus employees be removed from working on buses until the investigation is complete.

"We're going to keep these children safe," said Windward Schools Superintendent Lea Albert. "If the allegations are proven, we will not tolerate this kind of thing."

Albert told KITV that one of the Kailua Local bus workers was either fired or quit on Friday, a day after the second incident. It's unclear whether the other bus employee is still working.

"If these bus drivers are going to that extreme with our special education children riding a special education bus, then they need to not be driving these buses and something needs to be changed within the system," Martinez said.

The bus company did not return KITV's phone calls.