Hacienda "will accept nothing less than a full accounting of this absolutely horrifying situation, an unprecedented case that has devastated everyone involved, from the victim and her family to Hacienda staff at every level of our organisation," Gary Orman, a member of Hacienda's board of directors, said in the statement.
No one has been arrested in connection with the incident, and it's unclear whether police have identified any suspects.
Following the incident, a mother of another patient in the facility told KTVK she is sleeping in her daughter's room as she fears another attack.
Karina Cesena says her 22-year-old daughter has a traumatic brain injury and says she will continue sleeping in her room until the attacker is caught.
"I do not [know if my daughter was victimised], but I do ask her, and she can answer yes or no," Cesena told the news station. "She is not able to walk or talk yet, but she does understand."
About Hacienda HealthCare, Cesena said: "Trust has been broken. Trust has definitely been broken."
Other family members of patients told the news station that they'd noticed more security guards and a new protocol requiring male staffers to be accompanied by female staffers if they go into a female patient's room.
Hacienda HealthCare was founded five decades ago.
There have been reports of patient mistreatment. For example, an investigation in 2013 found that a staff member had made "inappropriate, sexual statements" about four clients. The staff member remarked that one client with intellectual disabilities had been placed in a sexual position.
The worker had also been observed watching clients touch themselves. The alleged incidents weren't reported to the facility's administrators until a month after they occurred.
That staff member was ultimately terminated, but the state found that the facility "failed to ensure clients . . . were treated with dignity".
