When I went on a hiking trip in 2012 in Montana, we camped for a few days, and the very first night I went outside the tent to bring my bag inside.. and I saw a huge black shadow next to the water, I was thinking WTF, and yeah it was clearly walking, I walked closer to have a better look and it was a man walking with some fishing equipment LOL, but he was big and it was so dark that I really legit for a second thought it might be bigfoot, I would say he was easily 6'8'', maybe even a little more, he was a big guy.
I can see why people can mistake things when its so dark like that, especially if you see such a large shape.