Kimberly Ruth Noyes is scheduled to appear in court Thursday on a second-degree murder charge. (CBC)

A charge of second-degree murder has been laid against Kimberly Ruth Noyes in connection with the death of a 12-year-old autistic boy in Grand Forks, B.C.

The body of John David Fulton was found Monday in Noyes' townhouse, just two doors away from his own home. The boy's family had reported to police that he suddenly went missing from his front yard Saturday.

Regional Crown counsel approved a charge of second-degree murder against Noyes Wednesday, RCMP said in a news release. The accused woman made an appearance via teleconference before a justice of the peace in Nelson, the release said.

Noyes is being held in custody until her next scheduled court appearance at 2 p.m. PT on Thursday at the Nelson courthouse, about 140 kilometres east of Grand Forks.

Noyes, 42, was not at her home when police found the boy's body. She was arrested Tuesday near the high school in Grand Forks without incident following an intensive search, police said.

The RCMP issued a public warning earlier Tuesday saying Noyes "does pose a threat to herself and possibly others due to her diagnosed state of mental health."

Noyes had suffered from dramatic mood swings brought on by bi-polar disorder and had been hospitalized briefly to treat the condition two years ago in Trail, B.C., former co-worker Kevin Thiessen told CBC News Wednesday.

Parents critical of police procedure

In a release sent to media Tuesday, the boy's family thanked police for their efforts but criticized the process involved when children are reported missing.

The body of John David Fulton, 12, was found Aug. 17 in a neighbour's home, two days after his family had reported him missing. (CBC)

"We would … like to express our concern with the lack of an Amber Alert in this investigation. We do not know if this could have saved Johnny’s life, nor do we wish to speculate, however, we feel strongly that any child with autism should automatically qualify as an Amber Alert," the release said.

The RCMP guidelines for Amber Alerts stipulate that police must know that a child has been abducted and is in imminent danger, according to the force's website.

"We can question as to what more we could have done but ... we're satisfied at the time we did [all we could]," RCMP Cpl. Dan Moskaluk said Wednesday.

Details about the cause of the boy's death have not been made public.