Mystery owl

We have a couple of owls hanging around here, and I don't know what species they are.

They're medium-large owls. At first I thought they were short-eared owls, but the photos on Google images don't match:

Short-eared owl from Google Images

Nor do they appear to be a Northern Hawk Owl.

Northern Hawk Owl from Google Images

Typically these mystery owls are audible (in pairs) in late evening, all through the night, and into early morning. Notice the yellow eyes and black beak. They have a harsh screeching cry, unlike the melodious Great Horned Owl's call. From my days as a field biologist, I'm very familiar with Great Grey owls, Barred owls, and Spotted owls, and know without question this isn't any of those species.

Yesterday morning I caught some shots of the mystery owl. I was on maximum zoom and frequently taking photos through a screened window in very early morning light (meaning, dim), so the photos aren't always clear or focused.

Below are the clearest shots I took. Any thoughts about the species?

UPDATE: You guys nailed it! It certainly seems to match with a juvenile Great Horned owl. In fact, here's a YouTube clip with the very sounds we've been hearing: begging cries. Since we have NOT been hearing any adult Great Horned owls nearby, I can only conclude these two youngsters (we always hear them in pairs) have just been booted out of the nest and are trying to figure out how to be adults.