Authorities have arrested three members of the neo-Nazi terror network The Base, including a missing Canadian soldier who used his military experience to provide weapons training to the group last fall.

The New York Times first reported that Patrik Mathews, a former Canadian Armed Forces reservist, was among the three arrested. The FBI confirmed Thursday that Mathews was arrested in Delaware by Baltimore FBI officers. The two other men were arrested in connection with Mathews.

Mathews went missing last summer after a Winnipeg Free Press investigation outed him as a recruiter for The Base in Canada.

The Base is an international neo-Nazi terror network with active cells around the world and affiliations to the domestic hate group Atomwaffen Division, which has been linked to several murders in the U.S.

A VICE investigation showed that Mathews hopped the border with the help of the neo-Nazi network. Once smuggled into the U.S. the 26-year-old man was hidden with the help of other members of The Base, including its leader. While in the U.S., Mathews continued to be active in The Base training other members in a paramilitary training camp held in Georgia this fall.

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Joshua Fisher-Birch, a research analyst for the Counter Extremism Project, told VICE that the arrest of The Base members was “welcome news, especially considering that it’s reported that they were armed and discussing attending upcoming pro-firearms protests in Virginia.”

“This is the perfect environment for the group to either attempt to recruit, or to try to encourage and spread disorder,” said Fisher-Birch. “Mathews has been missing for almost five months, which is ample time to pass on skills and training to his fellow neo-Nazis. The Base has repeatedly stated their support for extreme violence and terrorism. Measures taken to prevent them from organizing, training, and arming, are essential for public safety.”

Mathews was dismissed by the army after his connection to The Base was made public. During his time with the Canadian Forces he was provided with “rudimentary explosives training.” A prior VICE investigation into the Base showed that the group shared an online library which featured bomb- and chemical weapon-making manuals.

The men were arrested in the lead-up to a large second amendment protest taking place in Richmond, Virginia, this weekend.

The documents surrounding the arrest will reportedly be unsealed later Thursday.