An American woman pleaded guilty on Tuesday to conspiracy to commit murder, admitting in court that she had planned to carry out a mass shooting at a Canadian shopping mall on Valentine's Day in 2015.

Lindsay Kantha Souvannarath, 25, of Geneva, Ill., and two co-conspirators had plotted to shoot shoppers at a shopping center in Halifax, Nova Scotia. One of the others, Randall Steven Shepherd, pleaded guilty in November and was sentenced to 10 years in prison, according to the BBC.

Souvannarath and Shepherd were arrested a day before the planned attack. The other co-conspirator, James Gamble, was found dead of a self-inflicted gunshot wound shortly after.

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Souvannarath's plea came unexpectedly during a routine court hearing on Tuesday.

Those involved in the would-be attack were reportedly obsessed with death and mass shootings, such as the 1999 Columbine High School massacre.