RCMP arrived at the MacKenzie Sawmill after the man was observed on a surveillance camera inside the building late Monday night.
Cpl. Bert Paquet says that when the suspect saw police, he fled and dove into the river and swam to a log boom, where officers had a brief discussion with him before he broke into a floating shed and barricaded the door.
Paquet says the mill owner informed Mounties that the barge contained flammable items and others that could be used as weapons.
An emergency response team helped apprehend the man, who was arrested and transported to hospital as a precaution because of the amount of time he'd spent in the water.
Police are recommending charges of break and enter, along with theft and mischief.
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