Police say they are working to build a homicide case against the mother of two young children who have been missing for more than a week and are assumed dead.

Catherine Hoggle, the mother of 3-year-old Sarah and 2-year-old Jacob Hoggle, has been previously diagnosed with paranoid schizophrenia and has a long history of mental illness.

Hoggle ​was arrested Friday after being missing for five days. She has told police the children are safe but won’t say where they are, leading many to assume the worst.

Police Close In on Suspect in PA Cop Killing, Exchange Gunfire

WATCH: Motorcyclist T-Bones Two Cars, Lands Between Them!

Capt. Darren Francke of the Montgomery County Police joined Uma Pemmaraju on America's News Headquarters to discuss the disturbing case and the decision to shift to a homicide investigation.

Francke said that Hoggle originally stated that she put the children with "someone," but later changed her story to putting the children "somewhere."

He added that police have asked volunteers to help with the search of local areas to help bring closure to the children's father and the rest of the family.

Francke said you've got to hope the kids could be OK, but that based on his experience, some of Catherine Hoggle's comments and what her lawyers have and have not been able to disclose to police during the investigation, his belief is that this isn't going to end well.

Watch the clip from America's News Headquarters above.

Inside the Language of Terrorism: ISIS Code Words Include 'PB&J,' 'Rap Concert' and 'Rash'

WATCH: White House Fence-Jumper Sprints Across Lawn, Enters Front Doors