The FBI is investigating the recent death of a 3-year-old girl, who is thought to have been tossed from a moving vehicle by her mother on U.S. Highway 313 south of Hardin, as a homicide.
The agency sought a warrant Wednesday to search a pickup truck registered to Mary Agnes Leider, 24, of Billings and St. Xavier. She is the mother of Tenielle Ameryl Big Day, 3.
The child died Dec. 3 from blunt-force trauma from a “vehicular incident,” Big Horn County Coroner Terry Bullis said earlier.
FBI spokeswoman Deborah Bertram in Salt Lake City declined to comment Thursday on the search warrant application, but earlier she said agents were in the midst of an ongoing investigation. The FBI has provided few details about the case.
However, the FBI’s search warrant application filed in U.S. District Court in Billings gives an account of what it suspects happened based on interviews with witnesses. Court records did not indicate when a search would be undertaken.
The truck is a purple 1999 Dodge pickup registered to Mary Agnes Leider. The search seeks hair, fibers, bodily fluids containing DNA and any item related to the pickup’s operation, the application said. The pickup is at Big Horn County’s impound yard in Hardin.
Tenielle Big Day was “allegedly thrown from a moving vehicle,” Larry J. McGrail II, an FBI special agent, said in the court document.
In an interview with investigators on Dec. 3, Wally Leider said his sister, Mary Leider, had thrown her daughter out of the pickup while he was driving, the agent said.
Mary Leider was sitting in the front seat with Tenielle on her lap, Wally Leider told investigators. The girl was “quiet but awake” when Mary Leider “opened the front passenger door with her right hand, and threw (Big Day) out of the pickup,” Wally Leider told investigators.
Wally Leider immediately stopped and Mary Leider got out of the pickup, the agent said. Wally Leider walked behind the pickup, where he found Tenielle and knew she was dead. He then picked up the child, put her in the back seat and drove toward his mother’s house.
Mary Leider told officers that she had been driving around with her daughter and drinking with her brothers when her brothers began arguing on the way home. She said she told Wally Leider to slow down. At some point he stopped the pickup and she hit her head on the dashboard.
Mary Leider also told officers that before hitting her head, her daughter was on her lap but that she couldn’t remember what had happened to the child when the pickup stopped or how her daughter got injured.
Three days later, Mary Leider was booked into the Yellowstone County jail on a warrant from Billings Municipal Court for revocation of a suspended sentence for traffic violations. She was released on Dec. 9.
Law enforcement officers learned something had happened Dec. 3 when the Big Horn County Sheriff’s Office started getting calls at 4:06 a.m. from people who were distraught and crying. The calls were tracked to an area near mile marker 11 on Highway 313 on the Crow Reservation. Officers and an ambulance responded.
A deputy sheriff found Mary Leider and her brother, Arland Leider, sitting by the side of the road, “crying uncontrollably,” the agent said. “Mary told the deputy that her baby was ‘gone’ and had been hit by a vehicle,” he said.
As more officers arrived, the deputy was sent farther along the highway to respond to a 911 call about a deceased 3-year-old. There, the deputy was met by Wally Leider and Georgiana Denny, the mother of Mary, Wally and Arland Leider. Denny took the deputy to her car, where Tenielle Big Day’s body had been placed. The pickup truck also was there.
Denny told investigators that her three children had been out partying while Tenielle Big Day was with them. Mary Leider had repeatedly refused Denny’s calls and text messages to return home with the child, she told officers.
Denny then started driving toward Hardin on Highway 313, looking for them. She stopped when she saw Mary Leider’s pickup approaching and Wally Leider was driving. Wally Leider told his mother that “something was wrong” with Tenielle and that his sister had thrown the child from the pickup. Denny called for an ambulance and placed the child in her car.