La Brosse worked with the Montagnais people, translating and printing a book of prayers and catechism in the Montagnais dialect in 1767, one of the first books printed by a Canadian press. He is also believed to have miraculously stopped a forest fire, thereby earning the respect of the hitherto hostile Naskapi Indians. Upon Jean-Baptiste de La Brosse's death, darkness is said to have covered the Saguenay River, and in all the parishes where he had preached the bells began ringing without anyone going near them.
See also Folklore.