PERHAM, Minn. - William Hillman, the 21-year-old jailed in the deaths of a rural Perham mother and son this week, was declared mentally ill in 2016 in Cass County, Minn., and hospitalized in the St. Peter Regional Treatment Center for over a year, after attacking and threatening to kill his own mother, court documents show.

Hillman, who was 19 at the time, was charged with felony threats of violence, for threatening to beat and potentially kill his mother in an attack on her April 10, 2016, in her Pine River home. He was also charged with interfering with an emergency call and domestic assault.

A court-ordered evaluation by a psychologist found the Pine River man mentally incompetent for trial, and he was officially committed in June 2016 for inpatient treatment for schizophrenia, with possible attention deficit hyperactivity disorder and personality disorder.

Hillman's "very substantial thought disorder" grossly impaired his judgment, capacity to recognize reality, and to reason or understand, according to Dr. Charles Chmielewski's evaluation, dated May 13, 2016.

"He does pose a substantial likelihood of physical harm to others," Chmielewski wrote, concluding that it wasn't clear whether Hillman would be willing to take medication to treat his condition.

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According to court documents, including Chmielewski's report on Hillman:

Hillman's mother, Geneva Derbyshire, said he came into her room as she slept and "began to punch her and yelled profanities."

Police reports described, "redness, swelling, and a small cut on the left side of her cheek" from the attack.

Derbyshire said her son "was screaming delusional things," and "he kept telling me that I was hissing at him when he was in another room and I needed to stop."

She fled to a nearby gas station, "and when I got to the store he's my loving son again, and here Mom, here's your coat, I don't want you to be cold, and gives me my coat and my phone and left again."

She also said Hillman assaulted her on New Year's Eve after she returned home from celebrating. She said she suffered a fractured wrist and crushed right knuckle, and needed surgery to repair the damage. He also badly bruised her leg, she said.

"This has been ongoing for a very long time, like two years, and it's obvious that he's not on drugs, he's mentally ill and he needs a professional's help that I cannot give him and I cannot make him get," she said at the time.

In May 2017, Hillman pleaded guilty to the threats of violence charge and the other charges against him were dismissed. The parties in the case then agreed that the court would find him not guilty by reason of mental illness.

Hillman was eventually released from the St. Peter Regional Treatment Center in November 2017.

He's now in the Otter Tail County Jail, where he's been held since he was arrested Tuesday, April 17, as a suspect in the deaths discovered early that morning near Perham.

The Otter Tail County Sheriff's Office has identified the victims as 42-year-old Denise Mcfadzen and her son, 21-year-old Dalton Mcfadzen. Their bodies were found when deputies responded early Tuesday to a report of an assault at their home.

Investigators have said the deaths appear to be homicides, but have not released further details. Hillman is being held on two charges of second-degree homicide (with intent, but not premeditated), according to the sheriff's office and jail roster. He's expected to appear in court Thursday morning, April 19.