Matthew, a non-verbal man with autism, was sharing a state-funded emergency facility, Autism Plus, with four other young people. One of them had already attacked Matthew several times.

For months, Ms Thomas begged the Department of Human Services to have the perpetrator removed.

For months, little was done – despite three incidents, one involving police.

Then it was too late.

On the night of April 18, 2015, the co-resident escaped his carer and set upon Matthew in a toilet – the nature of the assault was so serious police later charged the youth with rape and assault.

Now Ms Thomas wants those responsible for letting her son down held to account.

"My son was assaulted and they want to get away with that," she said.

"They don't care how we feel. They let it happen many times. What is wrong with them? What is wrong with DHS and Autism Plus?"

Matthew Thomas was 20 when his parents, Maria and Peter, had to move him to the Westmeadows group house.

Just four months into his stay, on November 11, 2014, they were told their son had been sexually assaulted by another resident at the facility.

The Thomases were informed that a staff member had discovered another resident in bed with their son.

"They found Matthew is in bed with [the man] on the top ... according to the manager, fully clothed," Mrs Thomas said.

"I was shocked. How could it happen? I thought Matthew was safe in the facility. I felt sick, I nearly threw up."

The Thomases rang the department to complain and ask them and the facility to have the perpetrator removed. But nothing happened.

Less than a month later, on December 9, there was another incident in the house.

The resident broke away from a carer and rushed at Matthew shouting he was going to "hump" him. He was restrained before he could reach Matthew. Police were called and they issued a caution to the man for assault.

Ms Thomas said they again demanded the offender be removed from the facility.

"Peter and myself, we were just really scared, for the life of my son and his safety," she said.

"They don't care. They listen, but they don't do anything."

Matthew's health and state of mind deteriorated and for the first time he had a seizure.

"He didn't want us to go home," Ms Thomas said. "Every time we visited him, he was just grabbing our hand."

The family started visiting daily in a desperate attempt to protect their son, making a three-hour round trip to be by Matthew's side.

"I couldn't sleep because I was worried about my son's safety," she said.

"Every night I was waking up my husband ... at 2 o'clock in the morning I said to my husband, 'Pete, we have to go to the facility, we have to check Matthew, I feel something is going on there'."

Written correspondence seen by Fairfax Media shows the family was told by the department to visit less frequently because their visits were "confusing" their son.

The letter, dated January 23, 2015, a few months before Matthew was attacked for the third time, shows the department was aware of the family's fears for their son following the "attacks of a sexual nature by co-resident still living in the facility". The letter also notes the parents wanted the offender removed from the facility, but "would be reassured" if sensor alarms were installed on the doors.

However, it says, this safety measure could not be put in place due to lack of funding.

Eventually, the accused was moved to another part of the house, and locks and an alarm was put in Matthew's room.

But these failed to stop his attacker.

Matthew was assaulted for the third time on April 17, 2015 when the resident rushed at Matthew and ripped his shirt in front of multiple witnesses.

The next night, April 18, the resident came out of his room and attacked a carer, who fled and locked himself in an office. Then the youth attacked Matthew again.

The man was due to face the County Court on January 30, 2017 but Fairfax Media understands the case was dropped due to fears that the accused's disability was too serious to enable him to comprehend the charges against him.

Soon after the final incident, the resident was removed from the house.

Ms Thomas, who lost her husband in September 2015 after he suffered a heart attack while visiting Matthew, is now considering suing the facility and the department.

"My husband was eaten by the stress and, to be honest, it cost his life," Ms Thomas said.

Stuart Le Grand from Shine Lawyers, representing the family, said the question needed to be asked whether enough was done to protect Matthew.

A Department of Human Services spokeswoman said all the allegations were referred to the Disability Services Commissioner and reported to police.

"An independent review of Autism Plus was undertaken in October 2015. The focus of the review was on governance and management, including its obligations to comply with incident reporting obligations," she said. "Recommendations related to processes and systems and all actions were completed by June this year."

Autism Plus managing director Sandra Willis said the organisation took the care and safety of its clients very seriously.

"Robust policies and operational safeguards are always in place, and our employees are provided with the highest calibre of training that is very specific to our clients on the autism spectrum," Ms Willis said.

"Autism Plus have enjoyed a very positive relationship for many years with the Thomas family, and continue to work closely with them."

Kevin Stone, from VALID, an organisation for adults with intellectual disabilities, said both the department and the facility were responsible for failing Matthew.

He said the department could have removed the accused and the disability service should have done more to protect Matthew within the facility, including hiring more staff to supervise the residents.

Ms Thomas, who gave evidence at the Victorian Parliamentary Inquiry into Abuse in Disability Services, said she wanted to see those responsible held to account.

"I want someone out there to shoulder this responsibility about what happened to my son, not only for my child, but every disabled person who was abused who have no voice, no power."