Bern is mentioned in the Miner's Journal found on the bench in the main room of the mine. According to the journal, Bern is the partner of Hadrir, his old business partner and the author of the journal. Bern apparently persuaded Hadrir to help him prospect the abandoned mine, but as the job continued, the pair of miners continued to come up empty-handed, with the mine seemingly barren of precious metals or gems.
Then, on the 13th of First Seed, 4E 201, Bern asked Hadrir to head to Riften for supplies. The next entry in the journal is dated as the 29th of First Seed, and Hadrir returns to find no sign of Bern. Hadrir assumes that Bern decided to abandon his partner and vanish.
In reality, at some point between the 13th and the 29th of First Seed, Bern discovered a gold ore vein hidden behind the waterfall in the mine. As he worked on the vein, the tunnel collapsed, which either trapped or instantly killed him.