The Sonoma County District Attorney's Office says it has received additional information and will now begin reviewing the case.
The reaction from families of residents at the center is predictable. Their loved ones are among the most vulnerable in society.
"It's very upsetting that someone would do this to our family members who are pretty much helpless to defend themselves," Kathleen Miller said.
Miller heads the group of family members and advocates of those who live at the Sonoma Developmental Center, a home for people with severe disabilities. Miller's autistic son Dan is a resident. He was not a victim of the Taser attacks, but as president of the Parent Hospital Association, Miller wants answers.
"The families are going to want to know and be reassured that things are going to be taken seriously and handled in an effective, efficient manner," she said.
But were they? The investigation was conducted by the Office of Protective Services, the center's in-house police department.
Last September, the director of the center received a message on his answering machine. The anonymous caller said someone had a stun gun and was using it on patients.
The man was identified as psychiatric technician assistant Archie Millora. He worked at the center nearly 14 years.
Documents from the investigation reveal that officers confronted Millora the day after the phone call. They found the Taser in his car and a loaded Glock semi-automatic pistol plus a separate magazine with live rounds. Millora was placed on administrative leave but was never arrested.
A subsequent independent probe by the California Department of Public Health reveals that nurses examined and photographed patients in his care. They found suspicious abrasions on "the buttocks, thigh, arm and back" of 12 people. A forensic pathologist concluded that the marks were "strongly suggestive of electrical thermal burns," consistent with a Taser.
All of the reported victims have extreme difficulty communicating, but when questioned, one of them uttered the words "stun" and Millora's name which the incident report identified as "Staff A.".
Millora was eventually fired.
ABC7 News tried to talk to Millora but he did not respond to requests for an interview.
Court records show in April, Millora pleaded no contest to misdemeanor possession of a loaded firearm. He got probation and a $190 fine in lieu of jail time.
But Millora was never charged with the reported stun gun assaults -- charges that if convicted, could have given him serious prison time. It may never be known why because ABC7 News' requests for interviews with officials from the Sonoma Developmental Center and the OPS were denied.
With so much controversy surrounding the in-house police department, ABC7 News also wanted to know why it did not ask for help from the more seasoned investigators from the Sonoma County Sheriff's Office. A spokesperson for the Department of Developmental Services sent ABC7 News a statement saying, "The Sheriff's Office made the determination not to intercede." But the sheriff's department told ABC7 News, "We offered to assist in their investigation but we were told they didn't need our help."
Miller believes an outside law enforcement agency should be called in to investigate major crimes at the developmental center. She cannot believe there has been no arrest.
"It's devastating to the families," she said. "You have to let people know that we're serious about this. That's how you prevent further abuse."
The Sonoma County District Attorney's Office says it only went after Millora on the gun charge because the Office of Protective Services never referred the Taser assaults for criminal prosecution, but says it has received additional information and will now begin reviewing the case.