VATICAN CITY — Pope Francis declared Friday that Sister Maria Laura Mainetti, an Italian religious sister killed by three teenage girls in a Satanic sacrifice, was a martyr for the Catholic faith.

The 60-year-old Sister of the Cross was stabbed to death in 2000 by three teenage girls in a park in Chiavenna, Italy.

Sr. Mainetti's killers were convicted and imprisoned.

The girls knew the religious sister because she had taught them catechism. They lured her to the park by claiming that one of them needed to talk, because she had been raped and impregnated and was considering an abortion.

The three girls originally said the murder was "for a game," but later admitted they killed her as a demonic ritual.

In the park on the evening of June 6, 2000, the three girls made Sr. Mainetti kneel and shouted abuses at her. One girl beat the sister with a brick and another pushed her head repeatedly into a wall.

They took turns stabbing Mainetti 19 times with a kitchen knife. They had, according to Italian media reports, intended to stab her 18 times, six times each, to form by their violence the number 666.

Sr. Mainetti prayed throughout the attack and asked God to forgive the girls for their actions.

Sr. Mainetti was the superior of the Sisters of the Cross convent in Chiavenna, which was devoted to helping juvenile delinquents. The girls who killed Mainetti, however, had no prior history of crime or violence.

They confessed that they had originally planned to kill the parish priest, but decided that because he was larger, it would prove too difficult. Investigators said the girls’ notebooks were filled Satanic writings, and that they had made a blood oath some months earlier.

The killers have since been freed from prison, and have started families — changing their names and moving to large Italian cities, according to Corriere della Serra.  

Their victim was born Teresina Elsa Mainetti in Colico, Italy on August 20, 1939. She was the youngest of ten children; her mother died in childbirth. She entered the Congregation of the Sisters of the Cross at 18 years old.

She dedicated her life to children, young people, and families in the towns of Vasto, Rome, and Parma before moving to Chiavenna in 1984.

Sr. Mainetti was well known in her small town for her social and charitable commitment to dispossessed youth and poor people.

In 2008, Pope Benedict XVI praised Sr. Mainetti, who, he said, "with a total giving of self, sacrificed her life while praying for those who were attacking her."

Pope Francis also advanced June 19 the causes of four other men and women on the path to sainthood.

He approved miracles attributed to the causes of three Venerable Servants of God, who can now be beatified: Argentinian Bishop Mamerto Esquiú of the Order of Friars Minor (1826-1883); German Fr. Francis Mary of the Cross Jordan, founder of the Society of the Divine Savior (1848-1918); and Venezuelan layman and doctor Jose Gregorio Hernandez Cisneros (1864-1919).

The pope also declared the heroic virtue of Servant of God Maria de Jesus Elizondo Garcia, superior general of the Congregation of the Catechist Missionaries of the Poor. She was born in Durango, Mexico in 1908 and died in Monterrey on December 8, 1966.