I'm not certain what that is exactly, but i believe it is a bird. Probably some sort of owl. Try a birding website to get the exact species. The repetitive nature I heard and you described does not sound like elk. If it were some sort of small mammal, like a squirrel it would not continue all night. So like I said, best guess is its an owl.
UPDATE-because I'm a geek and it was eating at me- I'd now say it is a northern pygmy owl, given your location and the owl calls I was just listening to.
When placing a trail camera don't just look for a well used trail. What you want to do is look for a freshly used trail off by itself that goes from a north facing ridge, thick forest, brushy knob or some other similar bedding area to a food source. Don't forget water sources. Especially in the summer months the deer need water so look for a good trail going down too a creek surrounded by thick cover and place the camera 100 yards up from the water source.
Scent control is very important...