A 17-month-old-daughter in a stroller was pushed into the desert and left to die by her mother on an American Indian Reservation in Arizona. The mother has been sentenced to 20 years in prison.

US District Judge David Campbell said Ashley Denise Attson, 23, committed an “intentional, cold-hearted, horrendous killing of an innocent child,” imposing Monday the high end of a sentencing range detailed in a plea agreement with prosecutors.

Attson had pleaded guilty to second-degree murder in the September 2016 killing on the Navajo Nation. Her defense attorney, Ashley Adams, did not immediately return a call for comment.

Attson left her daughter in the desert for four days and nights before retrieving the body and burying it in an animal hole, the US Attorney’s Office for Arizona said Tuesday in a statement.

“Over the next few days, she met friends for ice cream and posted pictures of herself on Facebook,” the statement said.

The child was born with methamphetamine in her system and was in the custody of tribal social services most of her life before Attson regained custody about two months before her daughter was killed, prosecutors said.

US attorney’s spokesman Cosme Lopez declined to comment on the motive for the killing and said he could not provide additional information on circumstances of the child’s death.

Lopez also said policy prohibited release of the child’s name because she was a juvenile. Court documents refer to her as “Jane Doe.”