When two National Park Service rangers saw a car parked along the shoulder of the Blue Ridge Parkway near a man and a little girl walking down a steep embankment, they thought they were simply investigating illegal campers.

Minutes later, the man, Seth Pickering, began building a campfire out of underbrush, according to a criminal complaint. Unaware that the girl, Pickering's own 6-year-old daughter, had been reported missing, one of the rangers walked toward the pair near the road in North Carolina.

"It's going fine, nothing going on," Pickering said, according to the complaint.

Then, out of nowhere, Pickering turned away and lunged at his daughter, who was standing a few feet behind him.

The ranger heard a thud and a high-pitched grunt, the complaint said.

The girl with curly hair fell to the ground with a knife on her chest.

"Did you just stab her?" the ranger asked Pickering.

As he handcuffed her father, the other ranger tried to resuscitate Lila Pickering, but to no avail.

When asked why he killed his own daughter, the complaint states, Pickering said: "Now they will never be able to take her away from me. She's happier now. ... It's what she wanted."

Pickering had been in a custody fight over his daughter, who weeks earlier was temporarily placed under the care of a custodian for the Buncombe County Department of Health Services.

The complaint does not say why the girl was placed under protective care, but Pickering was allowed supervised visits.

On Friday, at about 5:20 p.m., Pickering was supposed to have one such visit with Lila. But, according to the complaint, he took his daughter without the custodian's permission.

"Seth, please don't do this, they will put you in jail," the custodian told Pickering as he was placing Lila in his vehicle, according to the complaint.

Pickering shook his head and drove off.

The custodian reported the girl missing to the Buncombe County Sheriff's Office.

Less than an hour later, the rangers happened upon Pickering's Dodge Avenger during a routine patrol.

In a recorded interview with a sheriff's detective, Pickering said he took his daughter to the parkway to go camping and was setting up a campsite when he saw the rangers, according to the complaint.

Shortly after one of the rangers approached him, Pickering said his daughter made him promise "that they would never take her away from me again," according to the complaint.

"I reacted the only way I knew that she could go to sleep without having to cry, 'Daddy I want to come home, '" Pickering told detectives. "I knew as soon as they showed up, they would take her away from me and never let me see her again."

Pickering, 36, has been charged with murder.

Investigators found two kitchen knife blocks in Pickering's home in Leicester, N.C.; each block was missing one knife, according to the complaint.

One set consists of knives with silver or metallic handles and a black, oval-shaped decorative peg where the handle joins the blade. The knife found on Lila's chest matched the knives found in Pickering's home, authorities said.

Autopsy results indicate that Lila was stabbed in the heart and a lung, according to media reports.

Pickering's estranged wife told the Asheville Citizen-Times that Lila was placed under protective care because her husband struck another woman. Seth Pickering moved to a duplex in Leicester about three weeks earlier and left the mobile home he'd shared with his wife, Ashley, the paper reported.

Hours before her daughter's death, Ashley Pickering said, a child protective services case worker from the county told her that her Lila "was happy and healthy and in a great home," the Citizen-Times reported.

"They were going to work on getting her back down here," said Ashley Pickering, who now lives in Florida.

But at about 2 a.m. Saturday, she got a call from a detective, who told her that her daughter had been killed and her estranged husband is the suspect, according to the paper.

"What they said to me just keeps playing in my head like a broken record," she told the Citizen-Times.

Ashley Pickering said she and her husband separated because he was abusive; they'd been locked in a custody battle for more than a year.

Still, she did not believe her daughter would be in danger. Seth Pickering was a loving father, she said, and his daughter adored him.

"She loved her daddy so much," Ashley Pickering told the paper. "She would jump in his lap and smile and laugh and be so happy when he was holding her."

Lila's relatives have set up a GoFundMe account to help pay for the cost of bringing her body to Florida.

More than $2,000 has been raised.

Seth Pickering, who is being held in the Buncombe County Detention Center, appeared in county court on Monday. Public defender LeeAnn Melton, who represented him there, was not immediately available for comment Wednesday.

The case has been transferred to federal court because the crime is alleged to have taken place on federal property.

Pickering is scheduled to appear before a federal judge next week, according to an online docket, which does not yet list a new attorney for Pickering.

On Monday, Lila's friends brought flowers to the first-grader's school and placed them at her desk, according to media reports.

Johnston Elementary School Principal Charlotte Hipps described Lila as a "precious" and "bubbly" girl.

Lila "just had a presence," Hipps told the Citizen-Times. "She was a very happy-go-lucky little girl, despite the circumstances in her life. It doesn't seem to ever get her down."

Her classmates also made cards for her.

"I hope you have a good time in heaven," one student wrote.