A Southern California woman who allegedly stabbed her three young children to death had reportedly been "unwell" for months, and the father of the kids is "devastated" after having pleaded with child services to get her help.

(Credit: Erik Denton)

LOS ANGELES MOTHER ARRESTED AFTER THREE TODDLERS FOUND STABBED TO DEATH

Investigators are working to establish a motive after the bodies of the children, ages 3, 2 and 6 months, were discovered by their grandmother when she returned home from work Saturday morning to their apartment in Los Angeles, the Los Angeles Times reported.

According to police, the scene was so gruesome that some of the initial responders are now getting counseling.

The mother of the children, 30-year-old Liliana Carrillo, was arrested hours later in Tulare County, about 200 miles north of Los Angeles, after igniting a massive manhunt.

She drove from the scene of the slayings in her car but ended up getting in an altercation that caused her to abandon that car and carjack another vehicle, LAPD Lt. Raul Jovel said.

LAPD Person of Interest Stabbing (LAPD)

The father of the children, Erick Denton, "is devastated," according to his cousin, Teri Miller, who spoke with Fox 11 Los Angeles on Sunday.

(Credit: Erik Denton)

Denton had been battling Carrillo, his ex-girlfriend, for custody of the boy and two girls for months and repeatedly reached out to the Department of Children and Family Services and police because he knew Carrillo "needed help," Miller said.

"Liliana was very sick, and this is not – she was not herself, and it's been going on for several months that she has been unwell," Miller told Fox 11 LA.

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Denton's relatives told the outlet that he received an emergency order in March granting him custody of the children but claimed he did not get any further help. Neighbors reportedly said the children were mostly seen with their grandmother, whom they believed to be their primary guardian.

"He's also frustrated with the system, because the system failed them," Miller said. "The system failed these kids."

Fox News' Paul Best contributed to this report.