Athena Strand: Tanner Horner strangled 7-year-old after hitting her with his van, arrest affidavit says

WISE COUNTY, Texas - The disturbing details of 7-year-old Athena Strand's death came to light Thursday in a newly filed arrest affidavit for contracted FedEx delivery driver Tanner Horner.

In a confession to investigators, Horner reportedly said he had finished delivering a package at Strand's home in Paradise. He said he was backing up his FedEx truck, when he accidentally hit Athena with the truck.

READ MORE: Athena Strand: What we know about Tanner Horner, the delivery driver who confessed to killing the 7-year-old

Horner told investigators that Athena was alive, but was not seriously hurt at the time. He said she was talking to him, even telling him her name.

The delivery driver said he panicked and put her into the van, according to court documents.

Horner then attempted to break the 7-year-old's neck to kill her. When that didn't work, he strangled the girl in the back of the FedEx van.

Wise County Sheriff Lane Akin told FOX News he plans to seek the death penalty for Strand’s murder.

The delivery driver said he strangled the girl because he was afraid she was going to tell her father that he hit her with the van.

Authorities say Horner then directed investigators to CR 4668 in Boyd, where he dumped her body in the water. The area is now marked with pink balloons, which is Strand's favorite color.

Strand was found dead on Dec. 2, two days after she was reported missing from the home.

The official cause of death for Athena has not been released at this time.

MORE ATHENA STRAND COVERAGE

The records also explain why Athen's stepmother, who was home alone with her, was not immediately aware the child was outside.

The stepmother was preparing dinner and Athena was sorting dirty laundry and staying in a converted shed that served as the bedroom for her and her stepsister next to the main home that is under renovation.

The arrest affidavit also details how investigators found Horner in the first place.

During the investigation, authorities learned that a package, which has since been identified as a Christmas gift for Athena, was delivered to her home.

Strand’s mother, Maitland Gandy, was emotional Thursday morning as she took her first look at the bright pink box of "You Can Be Anything" Barbies.

"This is the package, the first time I’m seeing it," she said. "This present, ordered out of innocence and love, is one she’ll never receive."

Investigators found the delivery was made by the company Big Topspin, which was contracted to deliver packages for FedEx.

"I was robbed of watching her grow up by a man that everyone was supposed to be able to trust, to do just one simple task: deliver a Christmas present and leave," Gandy added.

READ MORE: Athena Strand's alleged killing by FedEx driver raises security concerns about shipping service

BigTopsin employees helped investigators determine which van and driver were involved.

Video from the van that delivered the packages showed a young girl who looked like Athena in the van.

Investigators located Horner, where they say he confessed.

Horner has been charged with capital murder and aggravated kidnapping. His bond set at $1.5 million.

Fort Worth attorney Benson Varghese is representing Strand’s family for possible civil litigation.

"We don’t want another family to feel this kind of loss," he said. "We are investigating not just what FedEx’s responsibility might have been, but anyone else who was involved in the decisions that were made that led to this tragic loss."