A Canadian man accused in a failed shopping mall massacre plot in the Atlantic Canadian city of Halifax pleaded guilty on Tuesday and was sentenced to 10 years in prison, a prosecution spokeswoman said.

An American woman charged in the same case has pleaded not guilty and is expected to face trial in May, according to the court and prosecution.

The two were accused of planning a mass murder and suicide at a shopping center. They were arrested at the Halifax airport in February after the woman arrived from Illinois, allegedly to carry out the massacre.

Prosecution spokeswoman Chris Hansen said Randall Shepherd, who was 21 when he faced charges last year, pleaded guilty to conspiracy to commit murder at his court appearance and prosecutors and defense lawyers agreed on a 10-year prison sentence.

Shepherd and American Lindsay Souvannarath, who was 23 when she was charged last year, were accused of conspiracy to commit murder and arson as well making threats to cause harm or death through social media.

Shepherd and Souvannarath were arrested after police received a tip about their alleged plans to shoot as many people as possible at the Halifax Shopping Centre on Valentine’s Day and then kill themselves. A third man believed linked to the plot was found dead in a house in Halifax.

The two men were childhood friends in Halifax and they reportedly met Souvannarath online. All three admired the two teenagers who killed 12 students and a teacher in a high school shooting spree in Columbine, Colorado, in 1999, according to media reports.