A Boston charter school is working with several agencies to investigate an alleged sexual assault on a school bus, but parents are outraged because they say they learned of the incident through a Facebook post and not from the school.

Boston police told WFXT that they were notified of incident Nov. 3. WFXT learned Renaissance Boston Charter School failed to notify the Department of Elementary and Secondary Education, the agency which regulates the school and was supposed to be notified within two days of the incident being reported.

Several parents called WFXT because they have far too many questions and not enough answers.

“My stomach turned,” one parent said. “I was sick to my stomach. I was like, ‘How did they let this go on?’"

The mother of two, who didn't want to be identified, said she was first alerted to a Facebook post in the middle of the night.

The graphic post said in part, “I have a close friend whose son has been getting molested about ten times, mainly by another 6-year-old ... mainly on the bus."

>> Read more trending stories

The post contained many more graphic details of incidents on a school involving students at Boston Renaissance Charter School, one of the oldest charter schools in the city.

For this mom, and several others who contacted WFXT, the post was the first they heard of any alleged incident.

“I heard it on Facebook, that's how I heard it first, and then I got a phone call from the school," the mother said.

The school sent out an automated message around 8 a.m. Monday.

“We are aware of the Facebook post regarding an alleged incident on the school bus earlier this month," the message said.

“This has been happening since the beginning of November, why was no one informed until it went viral," a parent asked.

The post has been shared thousands of times.

Boston Renaissance posted what was said in the voice message to their website and they referred WFXT5 to the statement when we called with questions.

The statement said, in part: "The school leadership team took immediate action and followed appropriate legal protocols, contacting law enforcement immediately … We have taken this matter very seriously and taken all appropriate measures to ensure student safety."

But parents told WFXT they have no idea the scope of the investigation or how many children may be affected. The parents wondered if they would know anything at all were it not for a Facebook post.

Boston police referred the case to the Children's Advocacy Center because the child involved is less than 6 years old and therefore would not face criminal charges.

WFXT also reached out to the Department of Children and Families , which said it was made aware of the incident and is investigating.

Boston Public Schools doesn't regulate the school but does control transportation.

BPS sent a statement, which said: "The Boston Public Schools (BPS) is conducting an internal review into this matter. We are working with the charter school’s administration and our transportation provider to ensure that all protocols were properly followed. The safety and well-being of our students, and those we transport, are always a top priority of the BPS."

The Department of Children and Families also sent a statement, which read: "The Department received a report and we are investigating the incident, including notifying the district attorney."