The 21-year-old man accused of killing a mother and son in west-central Minnesota had been living with them for six weeks.
The charges against William Hillman state he had previously been diagnosed with mental illness, but had stopped taking his medication five months ago.
He allegedly attacked Denise, 42, and Dalton McFadzen, 21, with whom Hillman had been living for six weeks at a trailer in rural Perham.
Another of Denise McFadzen's sons found them early on Tuesday morning with brunt force trauma to their head caused by a pipe wrench.
Hillman was trying to flee by car at the time, but called police a short time later saying he had done a "bad thing" and needed to be arrested.
When interviewed by police, he said he'd come to live with the McFadzens six months earlier, but said they were "weird," before later saying: "I'm sorry. I'm sorry I did it."
Hillman told police he'd gone to sleep Monday and woke up when it was still dark. He said "everything went black" and didn't remember what happened next.
He'd previously been arrested for assaulting and threatening to kill his mother and had been committed to the Minnesota Security Hospital for 18 months having been diagnosed with schizophrenia.
He stopped taking his meds after going to live with his father in California, but returned home to Minnesota as his father was going to jail.
Prosecutors have charged him with two counts of second degree murder.