A 10-year-old Wisconsin girl with special needs was severely bruised after another student bit her several times on the school bus, according to her parents.

When Lynn Waldron-Moehle went to pick up her daughter, Lillian Waldron, from the bus stop on her way home from Langlade Elementary School in Green Bay on Monday, she noticed that the little girl was crying and holding onto her arm, Waldron-Moehle told ABC Green Bay affiliate WBAY.

Lilly, who Waldron-Moehle said is developmentally delayed, has the mannerisms of a 2-year-old and cannot speak, was inconsolable, so she decided to give her a bath to sooth her, she said.

"I was getting ready for the bath, and I took her sweatshirt off and that’s when I noticed the major bruising on her upper arm," Waldron-Moehle said.

Images taken of Lilly by her parents show the upper portion of her right arm covered in several large, red welts. The welts later turned into black and blue bruises, video taken by WBAY appears to show.

The child was bitten by another girl on the bus, which is dedicated to students with special needs, Lilly's father, Chad Waldron, told WBAY. The two children were sitting in the seat directly behind the driver, Waldron said, adding that he finds it hard to believe that the driver couldn't "hear anything going on or see anything."

"She can't tell them to stop," Waldron-Moehle said. "She couldn't get away, She's in a five-point harnessed car seat. She just had to sit there and take it, and the bus driver wasn't stopping it."

The district follows a student's individualized education program, so if a student's program requires that a monitor or aide be on the bus, then one is provided, Lori Blakeslee, director of communications and public relations for Green Bay Area Public Schools, told ABC News via email.

Green Bay Area Public Schools Superintendent Dr. Michelle Langenfeld expressed her "sincerest apologies to the student and family" in a statement.

"All students should be safe on the bus, and along with the administration, I deeply regret that this incident occurred," Langenfeld said.

Langerfeld and other administrators met with the family to address their concerns, and the school district is conducting an investigation, Langenfeld said.

Lilly will now ride in a van with two adults to and from school, her parents said.

The buses for the school district are contracted out, Kristin Rozek, community relations specialist for the school district told ABC News. Bus drivers are allowed to intervene in the event of an altercation, and all buses are equipped with video cameras, WBAY reported.

After watching the video, Langlade Elementary School Principal Jesse Brinkmann described the video as "gruesome and horrifying to look at -- that the girl was brutally biting my daughter's arm," Waldron-Moehle said.

Lilly's parents said the incident could have been avoided if the students had proper supervision. They told the local station that another incident occurred last year in which a boy undressed her. Blakeslee was unable to respond to requests for confirmation on this claim due to state and federal laws regarding student privacy, she said.

"If you can't keep an eye on these kids, and they are special needs, you need to bring somebody in you know to be watching if the bus driver can't do it," Waldron said.

The bus driver in this incident has been removed from all routes in the school district and "will never drive for the District in the future," Langenfeld said.

The school district will work with the bus company to "ensure appropriate processes and procedures are in place to prevent this from occurring in the future," Langenfeld said.

The girl who bit Lilly is no longer attending the school, Lilly's parents told WBAY. Blakeslee was unable to confirm this due to privacy concerns.