A 17-year-old stabbed her newborn baby 135 times and disposed of her body in a garbage can outside her home, authorities alleged Thursday.

Nicole Marie Beecroft was charged Thursday with first-degree murder. The charge carries a maximum sentence of life in prison. She was being held in a juvenile detention facility.

"She kills the baby and now her life will be changed forever," Washington County Attorney Doug Johnson said.

The Tartan High School senior told police she was in a "panic state" after giving birth to the girl on the floor of the laundry room in her home around 3 a.m. Monday, according to the criminal complaint filed in Washington County District Court. She told police she had seen the baby's finger move, and admitted stabbing the child, the complaint said.

An autopsy determined the infant had been born alive, but suffered numerous puncture wounds in the chest area and bled to death from 135 sharp-force injuries, the complaint said.

"We don't know what motivated her," Johnson said.

Johnson noted that the state's safe harbor law allows mothers to leave infants at any hospital within 72 hours of birth with no legal consequences.

"She could have walked away and the baby would have been adopted by a family that wanted it. Instead she destroys two lives: her own and the baby's," he said.

Police said the baby's body was inside a trash bag that had been placed in the garbage can outside Beecroft's suburban home. Inside the trash bag, investigators also found a black-handled knife and some towels, according to the complaint.

Authorities were tipped off Tuesday when an anonymous caller told police that a cashier at a Cub Foods grocery store in St. Paul had given birth to a stillborn baby and threw it in the garbage at her home. The store manager confirmed Beecroft was an employee there, but said she had called in sick the past two days. Police went to her home. Her mother told officers her daughter had been sick in bed the past two days, but had gone to work that day, according to the complaint.

Beecroft's mother, Kari Beecroft, allowed the officers to look in her daughter's room, where they found a bag containing adult diapers. The mother told police her daughter had been using them because she had been experiencing a very heavy period, the complaint said. The officers found a blood-soaked sanitary napkin or diaper in the bathroom garbage can.

While police secured the scene Tuesday night, other officers found Nicole Beecroft at the store where she worked. They took her back to the Oakdale Police Department, where she acknowledged she had given birth the day before. She said she had gone to the bathroom, but something didn't feel right, so she went to the laundry room and put a towel on the floor, and gave birth there. She initially claimed the girl was stillborn, and admitted discarding the child in the garbage can, the complaint said.

Police then got a search warrant, and recovered the body from the garbage can early Wednesday. Beecroft confessed when officers later confronted her at a hospital, the complaint said.

The girl's mother told police she didn't know her overweight daughter was pregnant.

The Beecroft family does not have a listed phone number.

An attorney will be appointed for her and bail will be set at her first court appearance Friday, Johnson said.

Johnson said Beecroft has told police the name of the person she believes is the father.

Oakdale police officer Michelle Stark said no one else was expected to be charged in the baby's death.

"Some early intervention possibly could have helped," Stark said.